Handoff for non-geosynchronous satellite communication

ABSTRACT

Various aspects of the disclosure relate to handoff of a user terminal in communication with a gateway through a satellite in a non-geosynchronous satellite communication system. In some aspects, a gateway and a user terminal use a satellite and beam transition table to determine when to handoff the user terminal from one beam to another and/or from one satellite to another. In some aspects, a user terminal sends capability information, location information, or other information to a gateway whereby, based on this information, the gateway generates a satellite and beam transition table and/or selects a handoff procedure for the user terminal. In some aspects, handoff of a user terminal to a different satellite involves the user terminal conducting satellite signal measurements and sending a measurement message to the gateway. In some aspects, the gateway generates a new satellite and beam transition table as a result of receiving a measurement message.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority to and the benefit of provisionalpatent application No. 62/156,063 filed in the U.S. Patent and TrademarkOffice on May 1, 2015, the entire content of which is incorporatedherein by reference.

BACKGROUND

Various aspects described herein relate to satellite communication, andmore particularly but not exclusively, to handoff for non-geosynchronoussatellite communication.

Conventional satellite-based communication systems include gateways andone or more satellites to relay communication signals between thegateways and one or more user terminals. A gateway is an earth stationhaving an antenna for transmitting signals to, and receiving signalsfrom, communication satellites. A gateway provides communication links,using satellites, for connecting a user terminal to other user terminalsor users of other communication systems, such as a public switchedtelephone network, the Internet and various public and/or privatenetworks. A satellite is an orbiting receiver and repeater used to relayinformation.

A satellite can receive signals from and transmit signals to a userterminal provided the user terminal is within the “footprint” of thesatellite. The footprint of a satellite is the geographic region on thesurface of the Earth within the range of signals of the satellite. Thefootprint is usually geographically divided into “beams,” through theuse of beamforming antennas. Each beam covers a particular geographicregion within the footprint. Beams may be directed so that more than onebeam from the same satellite covers the same specific geographic region.

Geosynchronous satellites have long been used for communication. Ageosynchronous satellite is stationary relative to a given location onthe Earth, and thus there is little timing shift and Doppler frequencyshift in radio signal propagation between a communication transceiver onthe Earth and the geosynchronous satellite. However, becausegeosynchronous satellites are limited to a geosynchronous orbit (GSO),which is a circle having a radius of approximately 42,164 km from thecenter of the Earth directly above the Earth's equator, the number ofsatellites that may be placed in the GSO is limited.

As alternatives to geosynchronous satellites, communication systemswhich utilize a constellation of satellites in non-geosynchronousorbits, such as low-earth orbits (LEO), have been devised to providecommunication coverage to the entire Earth or at least large parts ofthe Earth. In non-geosynchronous satellite-based systems, such as LEOsatellite-based systems, the satellites move relative to a communicationdevice (such as a gateway or a user terminal (UT)) on the ground. Thus,a UT may be handed-off from one satellite to another.

SUMMARY

The following presents a simplified summary of some aspects of thedisclosure to provide a basic understanding of such aspects. Thissummary is not an extensive overview of all contemplated features of thedisclosure, and is intended neither to identify key or critical elementsof all aspects of the disclosure nor to delineate the scope of any orall aspects of the disclosure. Its sole purpose is to present variousconcepts of some aspects of the disclosure in a simplified form as aprelude to the more detailed description that is presented later.

Aspects of the disclosure are directed to handoff for non-geosynchronoussatellite communication.

In one aspect, the disclosure provides an apparatus configured forcommunication that includes a memory device and a processing circuitcoupled to the memory device. The processing circuit is configured to:generate satellite and beam transition information that specifies a timeto start and a time to terminate communication with a particular beam ofa particular satellite; and send the satellite and beam transitioninformation to a user terminal.

Another aspect of the disclosure provides a method for communicationincluding: generating satellite and beam transition information thatspecifies a time to start and a time to terminate communication with aparticular beam of a particular satellite; and

sending the satellite and beam transition information to a user terminalAnother aspect of the disclosure provides an apparatus configured forcommunication. The apparatus including: means for generating satelliteand beam transition information that specifies a time to start and atime to terminate communication with a particular beam of a particularsatellite; and means for sending the satellite and beam transitioninformation to a user terminal.

Another aspect of the disclosure provides a non-transitorycomputer-readable medium storing computer-executable code, includingcode to: generate satellite and beam transition information thatspecifies a time to start and a time to terminate communication with aparticular beam of a particular satellite; and send the satellite andbeam transition information to a user terminal.

In one aspect, the disclosure provides an apparatus configured forcommunication that includes a memory device and a processing circuitcoupled to the memory device. The processing circuit is configured to:receive satellite and beam transition information that specifies a timeto start and a time to terminate communication with a particular beam ofa particular satellite; and perform handoff to the particular beam ofthe particular satellite based on the satellite and beam transitioninformation.

Another aspect of the disclosure provides a method for communicationincluding: receiving satellite and beam transition information thatspecifies a time to start and a time to terminate communication with aparticular beam of a particular satellite; and performing handoff to theparticular beam of the particular satellite based on the satellite andbeam transition information.

Another aspect of the disclosure provides an apparatus configured forcommunication. The apparatus including: means for receiving satelliteand beam transition information that specifies a time to start and atime to terminate communication with a particular beam of a particularsatellite; and means for performing handoff to the particular beam ofthe particular satellite based on the satellite and beam transitioninformation.

Another aspect of the disclosure provides a non-transitorycomputer-readable medium storing computer-executable code, includingcode to: receive satellite and beam transition information thatspecifies a time to start and a time to terminate communication with aparticular beam of a particular satellite; and perform handoff to theparticular beam of the particular satellite based on the satellite andbeam transition information.

These and other aspects of the disclosure will become more fullyunderstood upon a review of the detailed description, which follows.Other aspects, features, and implementations of the disclosure willbecome apparent to those of ordinary skill in the art, upon reviewingthe following description of specific implementations of the disclosurein conjunction with the accompanying figures. While features of thedisclosure may be discussed relative to certain implementations andfigures below, all implementations of the disclosure can include one ormore of the advantageous features discussed herein. In other words,while one or more implementations may be discussed as having certainadvantageous features, one or more of such features may also be used inaccordance with the various implementations of the disclosure discussedherein. In similar fashion, while certain implementations may bediscussed below as device, system, or method implementations it shouldbe understood that such implementations can be implemented in variousdevices, systems, and methods.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are presented to aid in the description ofaspects of the disclosure and are provided solely for illustration ofthe aspects and not limitations thereof.

FIG. 1 is a block diagram of an example communication system inaccordance with some aspects of the disclosure.

FIG. 2 is a block diagram of one example of a satellite network portal(SNP) of FIG. 1 in accordance with some aspects of the disclosure.

FIG. 3 is a block diagram of one example of a satellite of FIG. 1 inaccordance with some aspects of the disclosure.

FIG. 4 is a block diagram of one example of a user terminal of FIG. 1 inaccordance with some aspects of the disclosure.

FIG. 5 is a block diagram of one example of a user equipment of FIG. 1in accordance with some aspects of the disclosure.

FIG. 6 is a block diagram of an example communication system inaccordance with some aspects of the disclosure.

FIG. 7 is a diagram illustrating an example of inter-satellite handoffsignaling in accordance with some aspects of the disclosure.

FIG. 8 is a diagram illustrating another example of inter-satellitehandoff signaling in accordance with some aspects of the disclosure.

FIG. 9 is a diagram illustrating an example of generating and using asatellite and beam transition table in accordance with some aspects ofthe disclosure.

FIG. 10 is a diagram illustrating an example of using a satellite andbeam transition table in accordance with some aspects of the disclosure.

FIG. 11 is a diagram illustrating an example of signaling user terminalcapabilities in accordance with some aspects of the disclosure.

FIG. 12 is a diagram illustrating an example of using user terminalcapabilities in accordance with some aspects of the disclosure.

FIG. 13 is a diagram illustrating an example of signaling user terminallocation information in accordance with some aspects of the disclosure.

FIG. 14 is a diagram illustrating an example of using user terminallocation information in accordance with some aspects of the disclosure.

FIG. 15 is a diagram illustrating an example of user terminal handoffoperations in accordance with some aspects of the disclosure.

FIG. 16 is a diagram illustrating an example of SNP handoff operationsin accordance with some aspects of the disclosure.

FIG. 17 is a diagram illustrating another example of inter-satellitehandoff signaling in accordance with some aspects of the disclosure.

FIG. 18 is a diagram illustrating an example of signaling ephemerisinformation in accordance with some aspects of the disclosure.

FIG. 19 is a diagram illustrating an example of radio link failureoperations in accordance with some aspects of the disclosure.

FIG. 20 is a block diagram illustrating an example hardwareimplementation for an apparatus (e.g., an electronic device) that cansupport satellite-related communication in accordance with some aspectsof the disclosure.

FIG. 21 is a flowchart illustrating an example of a process involvinggeneration of satellite and beam transition information in accordancewith some aspects of the disclosure.

FIG. 22 is a block diagram illustrating an example hardwareimplementation for another apparatus (e.g., an electronic device) thatcan support satellite-related communication in accordance with someaspects of the disclosure.

FIG. 23 is a flowchart illustrating an example of a process involvinghandoff in accordance with some aspects of the disclosure.

DETAILED DESCRIPTION

The disclosure relates in some aspects to handoff of a user terminalthat is in communication with a satellite network portal (also referredto as a gateway) via a satellite of a non-geosynchronous satellitecommunication system. In some implementations, the satellitecommunication system is a low-earth orbit (LEO) satellite communicationsystem for communicating data, voice, video, or other information. Thesatellite network portal and the user terminal use a satellite and beamtransition table to determine when to handoff the user terminal from onebeam to another and/or from one satellite to another. In some aspects,the user terminal may send capability information, location information,or other information to the satellite network portal whereby, based onthis information, the satellite network portal generates a satellite andbeam transition table and/or selects a handoff procedure for the userterminal. The user terminal may also conduct satellite signalmeasurements and send a corresponding measurement message to thesatellite network portal. The satellite network portal may then generatea new satellite and beam transition table as a result of receiving themeasurement message. Various other aspects of the disclosure will alsobe described below in further detail.

Aspects of the disclosure are described in the following description andrelated drawings directed to specific examples. Alternate examples maybe devised without departing from the scope of the disclosure.Additionally, well-known elements will not be described in detail orwill be omitted so as not to obscure the relevant details of thedisclosure.

FIG. 1 illustrates an example of a satellite communication system 100which includes a plurality of satellites (although only one satellite300 is shown for clarity of illustration) in non-geosynchronous orbits,for example, low-earth orbits (LEO), an SNP 200 (e.g., corresponding toa satellite gateway) in communication with the satellite 300, aplurality of user terminals (UTs) 400 and 401 in communication with thesatellite 300, and a plurality of user equipment (UE) 500 and 501 incommunication with the UTs 400 and 401, respectively. Each UE 500 or 501may be a user device such as a mobile device, a telephone, a smartphone,a tablet, a laptop computer, a computer, a wearable device, a smartwatch, an audiovisual device, or any device including the capability tocommunicate with a UT. Additionally, the UE 500 and/or the UE 501 may bea device (e.g., access point, small cell, etc.) that is used tocommunicate to one or more end user devices. In the example illustratedin FIG. 1, the UT 400 and the UE 500 communicate with each other via abidirectional access link (having a forward access link and a returnaccess link), and similarly, the UT 401 and the UE 501 communicate witheach other via another bidirectional access link. In anotherimplementation, one or more additional UEs (not shown) may be configuredto receive only and therefore communicate with a UT only using a forwardaccess link. In another implementation, one or more additional UEs (notshown) may also communicate with the UT 400 or the UT 401.Alternatively, a UT and a corresponding UE may be integral parts of asingle physical device, such as a mobile telephone with an integralsatellite transceiver and an antenna for communicating directly with asatellite, for example.

The SNP 200 may have access to the Internet 108 or one or more othertypes of public, semiprivate or private networks. In the exampleillustrated in FIG. 1, the SNP 200 is in communication withinfrastructure 106, which is capable of accessing the Internet 108 orone or more other types of public, semiprivate or private networks. TheSNP 200 may also be coupled to various types of communication backhaul,including, for example, landline networks such as optical fiber networksor public switched telephone networks (PSTN) 110. Further, inalternative implementations the SNP 200 may interface to the Internet108, PSTN 110, or one or more other types of public, semiprivate orprivate networks without using the infrastructure 106. Still further,the SNP 200 may communicate with other SNPs, such as the SNP 201 throughthe infrastructure 106 or alternatively may be configured to communicateto the SNP 201 without using the infrastructure 106. The infrastructure106 may include, in whole or part, a network control center (NCC), asatellite control center (SCC), a wired and/or wireless core networkand/or any other components or systems used to facilitate operation ofand/or communication with the satellite communication system 100.

Communication between the satellite 300 and the SNP 200 in bothdirections are called feeder links, whereas communication between thesatellite and each of the UTs 400 and 401 in both directions are calledservice links. A signal path from the satellite 300 to a ground station,which may be the SNP 200 or one of the UTs 400 and 401, may begenerically called a downlink. A signal path from a ground station tothe satellite 300 may be generically called an uplink. Additionally, asillustrated, signals can have a general directionality such as a forwardlink and a return link (or reverse link). Accordingly, a communicationlink in a direction originating from the SNP 200 and terminating at theUT 400 through the satellite 300 is called a forward link, whereas acommunication link in a direction originating from the UT 400 andterminating at the SNP 200 through the satellite 300 is called a returnlink or a reverse link. As such, the signal path from the SNP 200 to thesatellite 300 is labeled a “Forward Feeder Link” 112 whereas the signalpath from the satellite 300 to the SNP 200 is labeled a “Return FeederLink” 114 in FIG. 1. In a similar manner, the signal path from each UT400 or 401 to the satellite 300 is labeled a “Return Service Link” 116whereas the signal path from the satellite 300 to each UT 400 or 401 islabeled a “Forward Service Link” 118 in FIG. 1.

A handoff controller 122 of the UT 401 and a handoff controller 124 ofthe SNP 200 cooperate to control handoff of the UT 401 from onesatellite or beam to another. Other components of the satellitecommunication system 100 may include corresponding handoff controllersas well. However, handoff controllers are only illustrated for the UT401 and the SNP 200 to reduce the complexity of FIG. 1.

The handoff controller 122 sends UT information 126 (e.g., including UTlocation and capabilities information) and measurement messages 128(e.g., including satellite measurement information) to the handoffcontroller 124. A satellite/beam transition information generatingmodule 130 of the handoff controller 124 generates satellite/beamtransition information (e.g., a table) indicative of handoff timing forthe UT 401. In some aspects, the satellite/beam transition informationgenerating module 130 may generate the satellite/beam transitioninformation based, at least in part, on the UT information 126 and themeasurement messages 128 received from the UT 401, satellite locationsover time (obtained from ephemeris data), satellite beam patterns, andsatellite beam turn-on and turn-off schedules. An information sendingmodule 132 sends this satellite/beam transition information 134 to thehandoff controller 122 via the current satellite 300.

An information receiving module 136 of the handoff controller 122receives this satellite/beam transition information 134 via the currentsatellite 300. A satellite/beam handoff module 138 of the handoffcontroller 122 can then control handoff of the UT 401 based on thereceived satellite/beam transition information.

FIG. 2 is an example block diagram of the SNP 200, which also can applyto the SNP 201 of FIG. 1. The SNP 200 is shown to include a number ofantennas 205, an RF subsystem 210, a digital subsystem 220, a PublicSwitched Telephone Network (PSTN) interface 230, a Local Area Network(LAN) interface 240, an SNP interface 245, and an SNP controller 250.The RF subsystem 210 is coupled to the antennas 205 and to the digitalsubsystem 220. The digital subsystem 220 is coupled to the PSTNinterface 230, to the LAN interface 240, and to the SNP interface 245.The SNP controller 250 is coupled to the RF subsystem 210, the digitalsubsystem 220, the PSTN interface 230, the LAN interface 240, and theSNP interface 245.

The RF subsystem 210, which may include a number of RF transceivers 212,an RF controller 214, and an antenna controller 216, may transmitcommunication signals to the satellite 300 via a forward feeder link301F, and may receive communication signals from the satellite 300 via areturn feeder link 301R. Although not shown for simplicity, each of theRF transceivers 212 may include a transmit chain and a receive chain.Each receive chain may include a low noise amplifier (LNA) and adown-converter (e.g., a mixer) to amplify and down-convert,respectively, received communication signals in a well-known manner. Inaddition, each receive chain may include an analog-to-digital converter(ADC) to convert the received communication signals from analog signalsto digital signals (e.g., for processing by the digital subsystem 220).Each transmit chain may include an up-converter (e.g., a mixer) and apower amplifier (PA) to up-convert and amplify, respectively,communication signals to be transmitted to the satellite 300 in awell-known manner. In addition, each transmit chain may include adigital-to-analog converter (DAC) to convert the digital signalsreceived from the digital subsystem 220 to analog signals to betransmitted to the satellite 300.

The RF controller 214 may be used to control various aspects of a numberof RF transceivers 212 (e.g., selection of the carrier frequency,frequency and phase calibration, gain settings, and the like). Theantenna controller 216 may control various aspects of the antennas 205(e.g., beamforming, beam steering, gain settings, frequency tuning, andthe like).

The digital subsystem 220 may include a number of digital receivermodules 222, a number of digital transmitter modules 224, a baseband(BB) processor 226, and a control (CTRL) processor 228. The digitalsubsystem 220 may process communication signals received from the RFsubsystem 210 and forward the processed communication signals to thePSTN interface 230 and/or the LAN interface 240, and may processcommunication signals received from the PSTN interface 230 and/or theLAN interface 240 and forward the processed communication signals to theRF subsystem 210.

Each digital receiver module 222 may correspond to signal processingelements used to manage communication between the SNP 200 and the UT400. One of the receive chains of RF transceivers 212 may provide inputsignals to multiple digital receiver modules 222. A number of digitalreceiver modules 222 may be used to accommodate all of the satellitebeams and possible diversity mode signals being handled at any giventime. Although not shown for simplicity, each digital receiver module222 may include one or more digital data receivers, a searcher receiver,and a diversity combiner and decoder circuit. The searcher receiver maybe used to search for appropriate diversity modes of carrier signals,and may be used to search for pilot signals (or other relatively fixedpattern strong signals).

The digital transmitter modules 224 may process signals to betransmitted to the UT 400 via the satellite 300. Although not shown forsimplicity, each digital transmitter module 224 may include a transmitmodulator that modulates data for transmission. The transmission powerof each transmit modulator may be controlled by a corresponding digitaltransmit power controller (not shown for simplicity) that may (1) applya minimum level of power for purposes of interference reduction andresource allocation and (2) apply appropriate levels of power whenneeded to compensate for attenuation in the transmission path and otherpath transfer characteristics.

The control processor 228, which is coupled to the digital receivermodules 222, the digital transmitter modules 224, and the basebandprocessor 226, may provide command and control signals to effectfunctions such as, but not limited to, signal processing, timing signalgeneration, power control, handoff control, diversity combining, andsystem interfacing.

The control processor 228 may also control the generation and power ofpilot, synchronization, and paging channel signals and their coupling tothe transmit power controller (not shown for simplicity). The pilotchannel is a signal that is not modulated by data, and may use arepetitive unchanging pattern or non-varying frame structure type(pattern) or tone type input. For example, the orthogonal function usedto form the channel for the pilot signal generally has a constant value,such as all 1's or 0's, or a well-known repetitive pattern, such as astructured pattern of interspersed 1's and 0's.

The baseband processor 226 is well known in the art and is therefore notdescribed in detail herein. For example, the baseband processor 226 mayinclude a variety of known elements such as (but not limited to) coders,data modems, and digital data switching and storage components.

The PSTN interface 230 may provide communication signals to, and receivecommunication signals from, an external PSTN either directly or throughadditional infrastructure 106, as illustrated in FIG. 1. The PSTNinterface 230 is well known in the art, and therefore is not describedin detail herein. For other implementations, the PSTN interface 230 maybe omitted, or may be replaced with any other suitable interface thatconnects the SNP 200 to a ground-based network (e.g., the Internet).

The LAN interface 240 may provide communication signals to, and receivecommunication signals from, an external LAN. For example, the LANinterface 240 may be coupled to the Internet 108 either directly orthrough additional infrastructure 106, as illustrated in FIG. 1. The LANinterface 240 is well known in the art, and therefore is not describedin detail herein.

The SNP interface 245 may provide communication signals to, and receivecommunication signals from, one or more other SNPs associated with thesatellite communication system 100 of FIG. 1 (and/or to/from SNPsassociated with other satellite communication systems, not shown forsimplicity). For some implementations, the SNP interface 245 maycommunicate with other SNPs via one or more dedicated communicationlines or channels (not shown for simplicity). For other implementations,the SNP interface 245 may communicate with other SNPs using the PSTN 110and/or other networks such as the Internet 108 (see also FIG. 1). For atleast one implementation, the SNP interface 245 may communicate withother SNPs via the infrastructure 106.

Overall SNP control may be provided by the SNP controller 250. The SNPcontroller 250 may plan and control utilization of the satellite 300'sresources by the SNP 200. For example, the SNP controller 250 mayanalyze trends, generate traffic plans, allocate satellite resources,monitor (or track) satellite positions, and monitor the performance ofthe SNP 200 and/or the satellite 300. The SNP controller 250 may also becoupled to a ground-based satellite controller (not shown forsimplicity) that maintains and monitors orbits of the satellite 300,relays satellite usage information to the SNP 200, tracks the positionsof the satellite 300, and/or adjusts various channel settings of thesatellite 300.

For the example implementation illustrated in FIG. 2, the SNP controller250 includes local time, frequency, and position references 251, whichmay provide local time or frequency information to the RF subsystem 210,the digital subsystem 220, and/or the interfaces 230, 240, and 245. Thetime or frequency information may be used to synchronize the variouscomponents of the SNP 200 with each other and/or with the satellite(s)300. The local time, frequency, and position references 251 may alsoprovide position information (e.g., ephemeris data) of the satellite(s)300 to the various components of the SNP 200. Further, although depictedin FIG. 2 as included within the SNP controller 250, for otherimplementations, the local time, frequency, and the position references251 may be a separate subsystem that is coupled to the SNP controller250 (and/or to one or more of the digital subsystem 220 and the RFsubsystem 210).

Although not shown in FIG. 2 for simplicity, the SNP controller 250 mayalso be coupled to a network control center (NCC) and/or a satellitecontrol center (SCC). For example, the SNP controller 250 may allow theSCC to communicate directly with the satellite(s) 300, for example, toretrieve ephemeris data from the satellite(s) 300. The SNP controller250 may also receive processed information (e.g., from the SCC and/orthe NCC) that allows the SNP controller 250 to properly aim its antennas205 (e.g., at the appropriate satellite(s) 300), to schedule beamtransmissions, to coordinate handoffs, and to perform various otherwell-known functions.

The SNP controller 250 may include one or more of a processing circuit232, a memory device 234, or a handoff controller 236 that independentlyor cooperatively perform handoff-related operations for the SNP 200 astaught herein. In an example implementation, the processing circuit 232is configured (e.g., programmed) to perform some or all of theseoperations. In another example implementation, the processing circuit232 (e.g., in the form of a processor) executes code stored in thememory device 234 to perform some or all of these operations. In anotherexample implementation, the handoff controller 236 is configured (e.g.,programmed) to perform some or all of these operations. Althoughdepicted in FIG. 2 as included within the SNP controller 250, for otherimplementations, one or more of the processing circuit 232, the memorydevice 234, or the handoff controller 236 may be a separate subsystemthat is coupled to the SNP controller 250 (and/or to one or more of thedigital subsystem 220 and the RF subsystem 210).

FIG. 3 is an example block diagram of the satellite 300 for illustrativepurposes only. It will be appreciated that specific satelliteconfigurations can vary significantly and may or may not includeon-board processing. Further, although illustrated as a singlesatellite, two or more satellites using inter-satellite communicationmay provide the functional connection between the SNP 200 and the UT400. It will be appreciated that the disclosure is not limited to anyspecific satellite configuration and any satellite or combinations ofsatellites that can provide the functional connection between the SNP200 and UT 400 can be considered within the scope of the disclosure. Inone example, the satellite 300 is shown to include a forward transponder310, a return transponder 320, an oscillator 330, a controller 340,forward link antennas 351 and 352(1)-352(N), and return link antennas362 and 361(1)-361(N). The forward transponder 310, which may processcommunication signals within a corresponding channel or frequency band,may include a respective one of first bandpass filters 311(1)-311(N), arespective one of first low noise amplifiers (LNAs) 312(1)-312(N), arespective one of frequency converters 313(1)-313(N), a respective oneof second LNAs 314(1)-314(N), a respective one of second bandpassfilters 315(1)-315(N), and a respective one of power amplifiers (PAs)316(1)-316(N). Each of the PAs 316(1)-316(N) is coupled to a respectiveone of antennas 352(1)-352(N), as shown in FIG. 3.

Within each of respective forward paths FP(1)-FP(N), the first bandpassfilter 311 passes signal components having frequencies within thechannel or frequency band of the respective forward path FP, and filterssignal components having frequencies outside the channel or frequencyband of the respective forward path FP. Thus, the pass band of the firstbandpass filter 311 corresponds to the width of the channel associatedwith the respective forward path FP. The first LNA 312 amplifies thereceived communication signals to a level suitable for processing by thefrequency converter 313. The frequency converter 313 converts thefrequency of the communication signals in the respective forward path FP(e.g., to a frequency suitable for transmission from the satellite 300to the UT 400). The second LNA 314 amplifies the frequency-convertedcommunication signals, and the second bandpass filter 315 filters signalcomponents having frequencies outside of the associated channel width.The PA 316 amplifies the filtered signals to a power level suitable fortransmission to the UTs 400 via a respective antenna 352. The returntransponder 320, which includes a number N of return paths RP(1)-RP(N),receives communication signals from the UT 400 along the return servicelink 302R via the antennas 361(1)-361(N), and transmits communicationsignals to the SNP 200 along the return feeder link 301R via one or moreof the antennas 362. Each of the return paths RP(1)-RP(N), which mayprocess communication signals within a corresponding channel orfrequency band, may be coupled to a respective one of the antennas361(1)-361(N), and may include a respective one of first bandpassfilters 321(1)-321(N), a respective one of first LNAs 322(1)-322(N), arespective one of frequency converters 323(1)-323(N), a respective oneof second LNAs 324(1)-324(N), and a respective one of second bandpassfilters 325(1)-325(N).

Within each of the respective return paths RP(1)-RP(N), the firstbandpass filter 321 passes signal components having frequencies withinthe channel or frequency band of the respective return path RP, andfilters signal components having frequencies outside the channel orfrequency band of the respective return path RP. Thus, the pass band ofthe first bandpass filter 321 may for some implementations correspond tothe width of the channel associated with the respective return path RP.The first LNA 322 amplifies all the received communication signals to alevel suitable for processing by the frequency converter 323. Thefrequency converter 323 converts the frequency of the communicationsignals in the respective return path RP (e.g., to a frequency suitablefor transmission from the satellite 300 to the SNP 200). The second LNA324 amplifies the frequency-converted communication signals, and thesecond bandpass filter 325 filters signal components having frequenciesoutside of the associated channel width. Signals from the return pathsRP(1)-RP(N) are combined and provided to the one or more antennas 362via a PA 326. The PA 326 amplifies the combined signals for transmissionto the SNP 200.

The oscillator 330, which may be any suitable circuit or device thatgenerates an oscillating signal, provides a forward local oscillatorsignal LO(F) to the frequency converters 313(1)-313(N) of the forwardtransponder 310, and provides a return local oscillator signal LO(R) tothe frequency converters 323(1)-323(N) of the return transponder 320.For example, the LO(F) signal may be used by the frequency converters313(1)-313(N) to convert communication signals from a frequency bandassociated with the transmission of signals from the SNP 200 to thesatellite 300 to a frequency band associated with the transmission ofsignals from the satellite 300 to the UT 400. The LO(R) signal may beused by the frequency converters 323(1)-323(N) to convert communicationsignals from a frequency band associated with the transmission ofsignals from the UT 400 to the satellite 300 to a frequency bandassociated with the transmission of signals from the satellite 300 tothe SNP 200.

The controller 340, which is coupled to the forward transponder 310, thereturn transponder 320, and the oscillator 330, may control variousoperations of the satellite 300 including (but not limited to) channelallocations. In one aspect, the controller 340 may include a memory (notshown) coupled to a processing circuit (e.g., a processor). The memorymay include a non-transitory computer-readable medium (e.g., one or morenonvolatile memory elements, such as an EPROM, an EEPROM, a Flashmemory, a hard drive, etc.) storing instructions that, when executed bythe processing circuit, cause the satellite 300 to perform operationsincluding (but not limited to) those described herein.

An example of a transceiver for use in the UT 400 or the UT 401 isillustrated in FIG. 4. In FIG. 4, at least one antenna 410 is providedfor receiving forward link communication signals (e.g., from thesatellite 300), which are transferred to an analog receiver 414, wherethey are down-converted, amplified, and digitized. A duplexer element412 is often used to allow the same antenna to serve both transmit andreceive functions. Alternatively, a UT transceiver may employ separateantennas for operating at different transmit and receive frequencies.

The digital communication signals output by the analog receiver 414 aretransferred to at least one digital data receiver 416A and at least onesearcher receiver 418. Additional digital data receivers (e.g., asrepresented by a digital data receiver 416N) can be used to obtaindesired levels of signal diversity, depending on the acceptable level oftransceiver complexity, as would be apparent to one skilled in therelevant art.

At least one user terminal control processor 420 is coupled to thedigital data receivers 416A-416N and the searcher receiver 418. Thecontrol processor 420 provides, among other functions, basic signalprocessing, timing, power and handoff control or coordination, andselection of frequency used for signal carriers. Another basic controlfunction that may be performed by the control processor 420 is theselection or manipulation of functions to be used for processing varioussignal waveforms. Signal processing by the control processor 420 caninclude a determination of relative signal strength and computation ofvarious related signal parameters. Such computations of signalparameters, such as timing and frequency may include the use ofadditional or separate dedicated circuitry to provide increasedefficiency or speed in measurements or improved allocation of controlprocessing resources.

The outputs of the digital data receivers 416A-416N are coupled todigital baseband circuitry 422 within the UT 400. The digital basebandcircuitry 422 includes processing and presentation elements used totransfer information to and from the UE 500 as shown in FIG. 1, forexample. Referring to FIG. 4, if diversity signal processing isemployed, the digital baseband circuitry 422 may include a diversitycombiner and decoder (not shown). Some of these elements may alsooperate under the control of, or in communication with, a controlprocessor 420.

When voice or other data is prepared as an output message or acommunication signal originating with the UT 400, the digital basebandcircuitry 422 is used to receive, store, process, and otherwise preparethe desired data for transmission. The digital baseband circuitry 422provides this data to a transmit modulator 426 operating under thecontrol of the control processor 420. The output of the transmitmodulator 426 is transferred to a power controller 428 which providesoutput power control to a transmit power amplifier 430 for finaltransmission of the output signal from the antenna 410 to a satellite(e.g., the satellite 300).

In FIG. 4, the UT transceiver also includes a memory 432 associated withthe control processor 420. The memory 432 may include instructions forexecution by the control processor 420 as well as data for processing bythe control processor 420. In the example illustrated in FIG. 4, thememory 432 may include instructions for performing time or frequencyadjustments to be applied to an RF signal to be transmitted by the UT400 via the return service link to the satellite 300.

In the example illustrated in FIG. 4, the UT 400 also includes optionallocal time, frequency and/or position references 434 (e.g., a GPSreceiver), which may provide local time, frequency and/or positioninformation to the control processor 420 for various applications,including, for example, time or frequency synchronization for the UT400.

The digital data receivers 416A-416N and the searcher receiver 418 areconfigured with signal correlation elements to demodulate and trackspecific signals. The searcher receiver 418 is used to search for pilotsignals, or other relatively fixed pattern strong signals, while thedigital data receivers 416A-416N are used to demodulate other signalsassociated with detected pilot signals. However, a digital data receiver416 can be assigned to track the pilot signal after acquisition toaccurately determine the ratio of signal chip energies to signal noise,and to formulate pilot signal strength. Therefore, the outputs of theseunits can be monitored to determine the energy in, or frequency of, thepilot signal or other signals. These receivers also employ frequencytracking elements that can be monitored to provide current frequency andtiming information to the control processor 420 for signals beingdemodulated.

The control processor 420 may use such information to determine to whatextent the received signals are offset from the oscillator frequency,when scaled to the same frequency band, as appropriate. This and otherinformation related to frequency errors and frequency shifts can bestored in a storage or memory element (e.g., the memory 432) as desired.

The control processor 420 may also be coupled to the UE interfacecircuitry 450 to allow communication between the UT 400 and one or moreUEs. The UE interface circuitry 450 may be configured as desired forcommunication with various UE configurations and accordingly may includevarious transceivers and related components depending on the variouscommunication technologies employed to communicate with the various UEssupported. For example, the UE interface circuitry 450 may include oneor more antennas, a wide area network (WAN) transceiver, a wirelesslocal area network (WLAN) transceiver, a Local Area Network (LAN)interface, a Public Switched Telephone Network (PSTN) interface and/orother known communication technologies configured to communicate withone or more UEs in communication with the UT 400.

The control processor 420 may include one or more of a processingcircuit 442, a memory device 444, or a handoff controller 446 thatindependently or cooperatively perform handoff-related operations forthe UT 400 as taught herein. In an example implementation, theprocessing circuit 442 is configured (e.g., programmed) to perform someor all of these operations. In another example implementation, theprocessing circuit 442 (e.g., in the form of a processor) executes codestored in the memory device 444 to perform some or all of theseoperations. In another example implementation, the handoff controller446 is configured (e.g., programmed) to perform some or all of theseoperations. Although depicted in FIG. 4 as included within the controlprocessor 420, for other implementations, one or more of the processingcircuit 442, the memory device 444, or the handoff controller 446 may bea separate subsystem that is coupled to the control processor 420.

FIG. 5 is a block diagram illustrating an example of the UE 500, whichalso can apply to the UE 501 of FIG. 1. The UE 500 as shown in FIG. 5may be a mobile device, a handheld computer, a tablet, a wearabledevice, a smart watch, or any type of device capable of interacting witha user, for example. Additionally, the UE 500 may be a network sidedevice that provides connectivity to various ultimate end user devicesand/or to various public or private networks. In the example shown inFIG. 5, the UE 500 may include a LAN interface 502, one or more antennas504, a wide area network (WAN) transceiver 506, a wireless local areanetwork (WLAN) transceiver 508, and a satellite positioning system (SPS)receiver 510. The SPS receiver 510 may be compatible with the GlobalPositioning System (GPS), the Global Navigation Satellite System(GLONASS) and/or any other global or regional satellite basedpositioning system. In an alternate aspect, the UE 500 may include aWLAN transceiver 508, such as a Wi-Fi transceiver, with or without theLAN interface 502, the WAN transceiver 506, and/or the SPS receiver 510,for example. Further, the UE 500 may include additional transceiverssuch as Bluetooth, ZigBee and other known technologies, with or withoutthe LAN interface 502, the WAN transceiver 506, the WLAN transceiver 508and/or the SPS receiver 510. Accordingly, the elements illustrated forthe UE 500 are provided merely as an example configuration and are notintended to limit the configuration of UEs in accordance with thevarious aspects disclosed herein.

In the example shown in FIG. 5, a processor 512 is connected to the LANinterface 502, the WAN transceiver 506, the WLAN transceiver 508 and theSPS receiver 510. Optionally, a motion sensor 514 and other sensors mayalso be coupled to the processor 512.

A memory 516 is connected to the processor 512. In one aspect, thememory 516 may include data 518 which may be transmitted to and/orreceived from the UT 400, as shown in FIG. 1. Referring to FIG. 5, thememory 516 may also include stored instructions 520 to be executed bythe processor 512 to perform the process steps for communicating withthe UT 400, for example. Furthermore, the UE 500 may also include a userinterface 522, which may include hardware and software for interfacinginputs or outputs of the processor 512 with the user through light,sound or tactile inputs or outputs, for example. In the example shown inFIG. 5, the UE 500 includes a microphone/speaker 524, a keypad 526, anda display 528 connected to the user interface 522. Alternatively, theuser's tactile input or output may be integrated with the display 528 byusing a touch-screen display, for example. Once again, the elementsillustrated in FIG. 5 are not intended to limit the configuration of theUEs disclosed herein and it will be appreciated that the elementsincluded in the UE 500 will vary based on the end use of the device andthe design choices of the system engineers.

Additionally, the UE 500 may be a user device such as a mobile device orexternal network side device in communication with but separate from theUT 400 as illustrated in FIG. 1, for example. Alternatively, the UE 500and the UT 400 may be integral parts of a single physical device.

In the example shown in FIG. 1, the two UTs 400 and 401 may conducttwo-way communication with the satellite 300 via return and forwardservice links within a beam coverage. A satellite may communicate withmore than two UTs within a beam coverage. The return service link fromthe UTs 400 and 401 to the satellite 300 may thus be a many-to-onechannel. Some of the UTs may be mobile while others may be stationary,for example. In a satellite communication system such as the exampleillustrated in FIG. 1, multiple UTs 400 and 401 within a beam coveragemay be time-division-multiplexed (TDM′ed),frequency-division-multiplexed (FDM′ed), or both.

At some point in time, a UT may need to be handed-off to anothersatellite (not shown in FIG. 1). Handoff may be caused by scheduledevents or unscheduled events.

Several examples of handoff due to scheduled events follow. Inter-beamand inter-satellite handoff may be caused by movement of the satellite,movement of the UT, or a satellite beam being turned off (e.g., due to aGeo-stationary satellite (GEO) restriction). Handoff also may be due toa satellite moving out of the SNP's range while the satellite is stillwithin the UT's line of sight.

Several examples of handoff due to nonscheduled events follow. Handoffmay be triggered by a satellite being obscured by an obstacle (e.g., atree). Handoff also may be triggered due to a drop in channel quality(e.g., signal quality) due to rain fade or other atmospheric conditions.

In some implementations, at a particular point in time, a particularsatellite may be controlled by a particular entity (e.g., a networkaccess controller, NAC) in an SNP. Thus, an SNP may have several NACs(e.g., implemented by the SNP controller 250 of FIG. 2), each of whichcontrols a corresponding one of the satellites controlled by the SNP. Inaddition, a given satellite may support multiple beams. Thus, over time,different types of handoff may occur.

In inter-beam handoff, a UT is handed-off from one beam of a satelliteto another beam of the satellite. For example, the particular beamserving a stationary UT may change over time as the serving satellitemoves.

In inter-satellite handoff, a UT is handed-off from the current servingsatellite (referred to as the source satellite) to another satellite(referred to as the target satellite). For example, a UT may behanded-off to the target satellite as the source satellite moves awayfrom the UT and the target satellite moves toward the UT.

Referring to FIG. 6, various aspects of the disclosure relate to handoffof a user terminal (UT) 602 in communication with a satellite networkportal (SNP) 604 through a satellite 606 in a non-geosynchronoussatellite communication system 600, such as a low-earth orbit (LEO)satellite communication system for data, voice, video, or othercommunication. The UT 602 is an example of the UT 400 or the UT 401 ofFIG. 1. The SNP 604 is an example of the SNP 200 or the SNP 201 ofFIG. 1. The satellite 606 is an example of the satellite 300 of FIG. 1.In some aspects, the SNP 604 and the UT 602 use a satellite and beamtransition table to determine when to handoff the UT 602 from one beamto another and/or from one satellite to another. For example, the UT 602may send information 608 (e.g., capability information, locationinformation, or other information) to the SNP 604. Based on thisinformation, the SNP 604 generates satellite and beam transitioninformation 610 and sends the information 610 to the UT 602 and/or theSNP 604 selects a handoff procedure for the UT 602. In some aspects,handoff of the UT 602 to a different satellite (a new serving satellite)involves the UT 602 conducting satellite signal measurements and sendinginformation 608 in the form of a measurement message to the SNP 604. Insome aspects, the SNP 604 generates a new satellite and beam transitiontable as a result of receiving the measurement message. In some aspects,the UT 602 receives satellite ephemeris information and uses theinformation to synchronize to a satellite. In some aspects, the UT 602invokes a radio link failure mode if the UT 602 loses connectivity to asatellite and/or beam.

As shown in FIG. 6, the SNP 604 includes network access controllers(NACs) 612, each of which interfaces with one or more radio frequency(RF) subsystems 614 for communicating with the UT 602 via the satellite606 (or some other satellite, not shown). The SNP 604 also includes acore network control plane (CNCP) 616, as well as a core network userplane (CNUP) 618 for communicating with one or more of a core network(e.g., 3G, 4G, 5G, etc.), an intranet, or an Internet 620. These andother aspects of the disclosure will be described in further detailbelow.

In some aspects, a handoff design may attempt to meet one or more of thefollowing objectives: minimize signaling during handoffs; minimize dataoutage during handoffs; or reduce reliance on the UT's knowledge of thesatellite ephemeris data, instead relying on the SNP's knowledge of thesatellite location and the UT location.

Several example aspects of a UT, an SNP, and a satellite that may beused in conjunction with handoff of a UT in accordance with theteachings herein will now be described.

Satellite ID

A Satellite Identifier (ID) is a unique ID of a particular satellitewithin a satellite system. The Satellite ID allows the satellite to beuniquely identified within the satellite system (e.g., by a UT). Toallow for a large satellite deployment, A Satellite ID could be 16 bitsor more. In some implementations, the Satellite ID is transmitted on anoverhead channel and is not required to be read immediately by the UT.The UT and the SNP may use a Satellite ID to index an ephemerisinformation table to locate the satellite and the projections of thesatellite's beams on the earth at a given time.

Beam ID

A Beam ID is a unique ID for a beam. The Beam ID allows a beam from agiven satellite to be uniquely identified (e.g., by a UT). In someaspects, a Beam ID may be detectable by a UT in a very short period oftime (e.g., the Beam ID may be a continuous signature used on the pilotof the beam). Thus, a UT might not need to decode an overhead message todiscover a Beam ID. In one non-limiting example, a Beam ID could include10 bits: 2 bits for an SNP ID (e.g., 2 bits may be sufficient to have aunique SNP visible by a UT; and the 4 values for the SNP ID could bereused across the globe); and 8 bits for the beam commanded by an SNP(e.g., an SNP controls approximately 10 satellites×16beams/satellite=160 beams/SNP=>8 bits to uniquely identify the beams). Adifferent number of bits could be used in other implementations. Also,spatial diversity of the satellites could be taken into consideration toreduce the number of bits.

UT Capabilities

A UT may exchange its capabilities with the SNP at connection time orsome other time. Several non-limiting example of UT capabilities follow.

A UT may be dual beam sense capable. Thus, one UT capability parameter(e.g., that takes a value of YES or NO) may indicate whether the UT iscapable of sensing more than one beam. For example, this capabilityparameter may indicate, while the UT is actively communicating using abeam of a particular satellite, whether the UT can sense and detect aBeam ID of another beam of the same satellite. In some implementations,this capability parameter can be used to indicate whether a UT cansupport two beams at the same time. A different number of beams (e.g.,three or more) could be supported in other implementations.

A UT may be dual satellite sense capable. Thus, another UT capabilityparameter (e.g., that takes a value of YES or NO) may indicate whetherthe UT is capable of sensing more than one satellite. For example, thiscapability parameter may indicate, while the UT is activelycommunicating using a beam of a particular satellite, whether the UT cansense and detect a Beam ID of another satellite. In someimplementations, this capability parameter can be used to indicatewhether a UT can support two satellites at the same time. A differentnumber of satellites (e.g., three or more) could be supported in otherimplementations.

As discussed in more detail below, an SNP may use the sense capabilityof a UT to determine what type of handoff to use for the UT. Forexample, if a UT can only support a single beam at a time, handoff couldsimply be based on the satellite and beam transition table. Conversely,if a UT can support multiple beams/satellites at a time, an SNP couldmonitor for a measurement message from a UT during handoff, whereby themeasurement message may affect how (e.g., when and/or where) the UT ishanded-off.

Another UT capability parameter may indicate the inter-beam tune time(e.g., in microseconds (μsec)) for a UT. This capability parameter mayindicate the time duration it takes for the UT to stop listening to abeam and start listening to another beam of the same satellite. Thus, insome aspects, the inter-beam tune time indicates how long it takes a UTto tune from one beam to another beam.

Another UT capability parameter may indicate the inter-satellite tunetime (e.g., in microseconds (μsec)) for a UT. This capability parametermay indicate the time duration it takes for the UT to stop listening toa beam on the current satellite and start listening to a beam of anothersatellite. Thus, in some aspects, the inter-satellite tune timeindicates how long it takes a UT to tune from one satellite to anothersatellite.

In some implementations, a tune time may be given as an upper bound. Forexample, a tune time may indicate the maximum amount of time that the UTis expected to take to tune from one beam or satellite to another.

In some implementations, a tune time may be described according to aformula. A non-limiting example of such a formula is: a+b*τ where, a isa constant that indicates the minimum time duration for theinter-satellite tuning, τ is the angular distance (in degrees) betweenthe current satellite and the target satellite, and b is the movementspeed of the UT's antenna in degrees of movement per millisecond.

Tuneaway Definitions

Signaling may be employed to allow a UT to tuneaway for inter-satelliteand inter-beam sensing. This signaling can be used to define tuneawayperiods for a UT to sense other beams of the same satellite or othersatellites.

Radio Link Failure

During normal operation, when a UT is handed-off from one satellite orbeam to another satellite or beam, the signaling for the handoff iscompleted between the SNP entity supporting the handoff and the UT. Ifthe UT loses communication with the SNP before the handoff signaling iscompleted, a radio link failure (RLF) may be declared (e.g., at the UT).In this case, the UT may employ an RLF recovery mechanism tore-establish communication with the SNP.

UT Location

A UT location reporting mechanism is employed for handoff processing andpaging so that the SNP will know the location of the UT (e.g., on acontinual or regular basis). In some implementations, a UT will havereliable global positioning system (GPS) positioning.

For stationary UTs, the UT location reporting mechanism may involve theUT sending a signaling message to the SNP that reports the location(e.g., the GPS coordinates) of the UT.

For mobile UTs (e.g., UTs on a ship or an airplane), the UT locationreporting mechanism may involve the UT sending a signaling message tothe SNP that reports the speed and direction of the UT. This allows theSNP to continuously estimate the location of the UT. Even for mobileUTs, the direction and speed information may be relatively stable if theUTs are carried by (e.g., attached to) relatively large vessels.

Also, via location-related signaling, the UT may be informed of thelocation drift allowed before a new location update message is needed.

Some implementations may employ thresholds for location tolerance. Someimplementations may employ GEO fencing. For example, if a UT is beyond adesignated boundary relative to a satellite and/or an SNP (e.g., the UTis a certain distance away), the UT may be configured to send a locationupdate to the SNP.

Ephemeris Transfer and Update Signaling

Ephemeris Transfer and Update signaling messages may be used to transfersatellite ephemeris data to the UTs. In some aspects, ephemeris dataincludes a geographic description of where a given satellite is at agiven point in time. This data may be used by the UT when it searchesfor the next satellite and beam (e.g., after the UT detects a Radio LinkFailure). For example, in some aspects, a UT may use the ephemeris datafor a given satellite to determine where to point the UT's antenna(antennas) at a given point in time. In some aspects, an SNP maytransmit a signaling message containing the satellite ephemeris data toall connected UTs (e.g., whenever there is an update). In some aspects,a UT may request satellite ephemeris data from the SNP (e.g., when theUT establishes a connection).

Satellite and Beam Transition Table

The SNP may generate a satellite and beam transition table that providesa list of satellites to which a UT may choose to handoff next. The tablealso may dictate exactly at what time the UT will switch over from onebeam of the next satellite to another. A beam table may indicate, for anumber of satellites, the beams to be used for each satellite. A beamtable also may indicate, for each beam, the frequency (e.g., the nominalradio frequency or frequency band) of the beam and the Beam ID of thebeam.

An SNP may define a satellite and beam transition table based on variousinformation. In some aspects, an SNP may define the table using thelocation (and speed and direction, if specified) of the UT. In someaspects, an SNP may define the table using satellite locations over timecalculated from ephemeris data. In some aspects, an SNP may define thetable based on information regarding whether certain beams and/orsatellites are turned off at certain times.

Table 1 below is a non-limiting example of a satellite and beamtransition table. TA_(beam) denotes the tune-away time from one beam toanother of the same satellite. In this example, the UT is to tune toSatellite 1, Beam 1 (on frequency F₁₁) from time a₁ to time b₁. The UTis to then tune to Satellite 1, Beam 2 (on frequency F₂₁) from timeb₁+TA_(beam) to time c₁, and so on.

In some implementations, the table may be sent in a signaling message bythe SNP to the UT it is serving, at any time before the UT is handed-offto the next satellite.

TABLE 1 Start Time End Time Satellite (Frame (Frame ID Beam ID Freqnumber) number) Satellite 1 Beam 1 F₁₁ a₁ b₁ Beam 2 F₂₁ b₁ + TA_(beam)c₁ . . . . . . . . . . . . Beam N F_(N1) m₁ + TA_(beam) n₁ Satellite 2Beam 1 F₁₂ a₂ b₂ Beam 2 F₂₂ b₂ + TA_(beam) c₂ . . . . . . . . . . . .Beam N F_(N2) m₂ + TA_(beam) n₂ . . . . . . . . . . . . . . .

In one example, the overhead of the satellite and beam transition tablemessage is as follows (assuming that there are two satellites listed inthe table): Satellite ID: 16 bits; Beam ID: 10 bits; Freq: Assuming 16beam frequencies per satellite, this field is 4 bits; and Start and EndTimes: 15 bits.

For the Start Time and End Time, these times can be specified in termsof Frame Numbers. The physical layer may specify the use of 10millisecond (ms) transmission frames for the system. Assuming that asatellite handoff takes place every 3 minutes, the number of frames thatcan be transmitted between handoffs is 18,000. Frame Numbers can bere-initialized from zero after every handoff. The number of bits thatare then required to specify the Frame Numbers is thus 15 bits in thisexample.

In the above example, the total overhead of the message would be 1020bits=128 bytes (approximately). The values of a₁, b₁, . . . , n₁,TA_(beam) would be specified.

If a maximum of 1000 active users can be served at any time by one beam,and if a beam overall downlink (DL) throughput is approximately 300Mbps, the overhead is given by: overhead=(128 bytes×numUsersBeam)/(totalbytes delivered by beam over 3 minutes), =(128bytes×1000)/(300×10⁶×3×60)=19×10⁻⁶ (approximately).

Inter-Satellite Handoff

FIGS. 7 and 8 illustrate examples of inter-satellite handoff. In theseexamples, the SNP includes a source NAC that controls a first satelliteand a target NAC that controls a second satellite. In each case, the UTinitially is connected to a source satellite (and, hence, the sourceNAC) and is subsequently handed-off to a target satellite (and, hence,the target NAC). A different number of NACs and satellites could besupported in other implementations. Also, in some implementations, acommon (i.e., the same) entity could support multiple satellites.

FIG. 7 is an example where a UT 702 does not send a measurement message.For example, the UT 702 might not support the sensing of multiplebeams/satellites or the UT 702 may determine that a measurement messageneed not be sent to an SNP 704. In this case, the UT 702 and the SNP 704rely on the existing satellite and beam transition table to determinewhen to transition to the next beam/satellite and where to transition(e.g., which beam, which frequency, which satellite). The UT 702 is anexample of the UT 400 or the UT 401 of FIG. 1. The SNP 704 is an exampleof the SNP 200 or the SNP 201 of FIG. 1.

A source NAC 706 sends control signaling 708 to the UT 702. This controlsignaling 708 may include, for example, measurement information andtuneaway control information (e.g., tuneaway definitions). In addition,packet data 710 is exchanged between the UT 702 and the source NAC 706.The source NAC 706 is an example of the NAC 612 of FIG. 6.

At some point in time a handoff is triggered 712. For example, thecurrent time may correspond to the time for a transition from onesatellite to the next indicated by the satellite and beam transitiontable.

Other handoff triggers may be employed as well. For example, the SNP 704(e.g., the source NAC 706) may decide autonomously that the UT 702 needsto be handed-off. Such a trigger may be due to, for example: the currentserving satellite is moving out of range of the UT 702; the satellite ismoving out of the range of the SNP 704, even if it may be within therange of the UT 702; or the beam serving the UT 702 will be blacked-outdue to GEO requirements.

In the event the UT 702 is capable of sensing another beam/satellitewhile connected to the first satellite, the UT 702 may search the signalstrength of the default satellite and beam for handoff. It may beassumed that the UT 702 has the location information of this satellitein order to do so. This location information can be obtained from thesatellite ephemeris data the UT 702 possesses. If the signal strength issatisfactory, the UT 702 does nothing and waits for the source NAC 706to start the inter-satellite handoff process.

Thus, in the example of FIG. 7, both the UT 702 and the source NAC 706will follow the table and commence the handoff to a new servingsatellite. To this end, the source NAC 706 will perform handoffprocessing 714. For example, the source NAC 706 may communicate with atarget NAC 716 to commence the handoff. In some aspects, this mayinvolve synchronizing the queues 718 (e.g., packet traffic queues)between the NACs 706 and 716. Also, as the time of the handoff is knownahead of time, the user queues can be transferred ahead of time. Thetarget NAC 716 is an example of the NAC 612 of FIG. 6.

The source NAC 706 then sends handoff signaling 720 to the UT 702. Insome aspects, this handoff signaling 720 may include information thatenables the UT 702 to communicate with the target NAC 716. In someaspects, this handoff signaling 720 may include a new satellite and beamtransition table (e.g., that the source NAC 706 received from the targetNAC 716).

The UT 702 then detaches 722 from the first satellite and synchronizesto the second satellite. To this end, the UT 702 may sendsynchronization signaling 724 for the second satellite to the target NAC716. In some aspects, this may involve the UT 702 performing a randomaccess procedure at the second satellite.

The UT 702 and the target NAC 716 may then exchange connection signaling726 and 728. In some aspects, this may involve the target NAC 716sending ephemeris information to the UT 702 and requesting a channelquality indicator from the UT 702. In some aspects, the UT 702 may usethe ephemeris information to synchronize with the second satellite.

Also, the various entities may perform various background operations toensure that packet forwarding is done properly and any needed clean-up(e.g., cache clean-up) is performed.

FIG. 8 is an example where a UT 802 does send a measurement message. Forexample, the UT 802 might determine that a measurement message needs tobe sent to an SNP 804 because the measured channel conditions (e.g.,signal strength) from the serving satellite or the target satellite areunacceptable (e.g., the signal strength is too low). In this case, theSNP 804 may generate a new satellite and beam transition table based onthe measurement message. The UT 802 and the SNP 804 will then use thenew satellite and beam transition table to determine when to transitionto the next beam/satellite and where to transition (e.g., which beam,which frequency, which satellite). The UT 802 is an example of the UT400 or the UT 401 of FIG. 1. The SNP 804 is an example of the SNP 200 orthe SNP 201 of FIG. 1.

As in FIG. 7, a source NAC 806 sends control signaling 808 to the UT802. This control signaling 808 may include, for example, measurementinformation and tuneaway control information (e.g., tuneawaydefinitions). In addition, packet data 810 is exchanged between the UT802 and the source NAC 806. The source NAC 806 is an example of the NAC612 of FIG. 6.

At some point in time a handoff is triggered 812. In some cases, thecurrent time corresponding to the time for a transition from onesatellite to the next as indicated by the satellite and beam transitiontable constitutes a handoff trigger. In some cases, a measurementmessage sent by the UT 802 indicating that a neighbor satellite ismaterially stronger (e.g., associated with a stronger received signalstrength) than a current serving satellite may constitute a handofftrigger.

Other handoff triggers may be employed as well. For example, the SNP 804(e.g., the source NAC 806) may decide autonomously that the UT 802 needsto be handed-off Such a trigger may be due to, for example: the currentserving satellite is moving out of range of the UT 802; the satellite ismoving out of the range of the SNP 804, even if it may be within therange of the UT 802; or the beam serving the UT 802 will be blacked-outdue to GEO requirements.

In the example of FIG. 8, the UT 802 is capable of sensing anotherbeam/satellite while connected to the first satellite. Thus, the UT 802may perform channel quality measurements (e.g., satellite signalstrength measurements). For example, the UT 802 may measure 814 thesignal strength from the current serving satellite (first satellite) andthe target satellite (second satellite).

The UT 802 then performs measurement processing 816 to determine, forexample, whether either channel quality is inadequate (e.g., signalstrength is too low). In the event either channel quality is inadequate,the UT 802 may elect to send a measurement message 818 to the source NAC806. This measurement message 818 may include, for example, the resultsof the measurements (e.g., signal strength in dB), an indication thatthe handoff time needs to be advanced (e.g., because the signal from thesource satellite is currently too low), an indication that the handofftime needs to be delayed (e.g., because the signal from the targetsatellite is currently too low), or some other indication.

Thus, similar to FIG. 7, the UT 802 may search the signal strength ofthe default satellite and beam for handoff. Again, it may be assumedthat the UT 802 has the location information of this satellite in orderto do so (e.g., obtained from the satellite ephemeris data the UT 802possesses). If the signal strength is not satisfactory, the UT 802 maysend a measurement message 818 to the source NAC 806 indicating asatellite different from the default one, to trigger the handoff processearly or delay it.

The source NAC 806 may thus make a decision to handoff the UT 802 to atarget satellite and a target NAC 820 based on the satellite and beamtransition table and on any measurement message 818 the source NAC 806receives from the UT 802. Thus, as indicated in FIG. 8, the source NAC806 will perform some handoff processing 822. For example, the sourceNAC 806 may decide, based on the measurement message 818, whether thehandoff time needs to be advanced (early handoff) or delayed (latehandoff), or whether some other satellite should be selected as thetarget. In addition, the source NAC 806 may communicate with a targetNAC 820 to commence the handoff. In some aspects, this may involvesynchronizing the queues 824 (e.g., packet traffic queues) between theNACs 806 and 820. The target NAC 820 is an example of the NAC 612 ofFIG. 6.

The source NAC 806 then sends handoff signaling 826 to the UT 802. Insome aspects, this handoff signaling 826 may include information thatenables the UT 802 to communicate with the target NAC 820. In someaspects, this handoff signaling 826 may include a new satellite and beamtransition table (e.g., that the source NAC 806 received from the targetNAC 820).

The UT 802 then detaches 828 from the first satellite and synchronizesto the second satellite. To this end, the UT 802 may sendsynchronization signaling 830 for the second satellite to the target NAC820.

The UT 802 and the target NAC 820 may then exchange connection signaling832 and 834. In some aspects, this may involve the target NAC 820sending ephemeris information to the UT 802 and requesting a channelquality indicator from the UT 802. Again, the various entities mayperform various background operations to ensure that packet forwardingis done properly and any needed clean-up (e.g., cache clean-up) isperformed.

With normal inter-satellite handoff, hybrid automatic repeat request(HARQ) processes may be terminated. However, the source NAC may knowexactly when the handoff will happen, therefore the source NAC canensure that the forward link data buffers are drained. Also, the gap fordata flow can be minimized since the time of handoff is known.

Inter-Beam Handoff

Inter-beam handoff is executed by the SNP and the UT synchronouslyaccording to the timeline specified in the satellite and beam transitiontable. Using the tuneaway periods or dual receive capability, the UTdetects the presence of the next beam specified in the satellite andbeam transition table. If the UT detects the next beam successfully, anormal inter-beam handoff is executed without any signaling between theUT and the SNP.

With normal inter-beam handoff, forward link HARQ processes may becarried over from one beam to the next. In addition, reverse assignmentsmay be cancelled as the UT hands-off from one beam to the next. Forexample, the UT may instead send new request messages to send reverselink data.

Exception Scenarios

If the UT loses the current serving beam before the expiration of thespecified time in the satellite and beam transition table, the UT entersinto RLF mode. In RLF mode, the UT may attempt to find an alternate beamor satellite (e.g., based on the ephemeris information at the UT). Forexample, the UT may attempt to connect to the next satellite that shouldbe serving the UT. If the UT successfully establishes anotherconnection, the UT can send signaling messages to the SNP to continuecommunication where the UT left off before the RLF.

While being served by a beam, the UT may fail to detect the next beamspecified in the satellite and beam transition table, but may detectanother beam. This may happen, for example, to a fast moving UT (e.g., aUT attached to an airplane). In this case, the UT may send a measurementmessage to initiate another handoff procedure. In addition, the UT mayalso send a position update if it has moved since the last time aposition update was sent. In response, the SNP may send an updatedsatellite and beam transition table. In this case, the UT follows theupdated table. Alternatively, the SNP may start a completely new handoffprocess.

Example Operations

With the above in mind, additional examples of operations that may beperformed by a UT and/or an SNP in support of handoff of the UT will nowbe described with respect to FIGS. 9-19.

FIG. 9 is a diagram illustrating an example of a process 900 forgenerating and using a satellite and beam transition table in accordancewith some aspects of the disclosure. The process 900 may take placewithin a processing circuit which may be located in an SNP or some othersuitable apparatus (device). In some implementations, the process 900represents operations performed by the SNP controller 250 of FIG. 2. Insome implementations, the process 900 represents operations performed bythe apparatus 2000 of FIG. 20 (e.g., by the processing circuit 2010). Ofcourse, in various aspects within the scope of the disclosure, theprocess 900 may be implemented by any suitable apparatus capable ofsupporting communication-related operations.

At block 902, an SNP (or other suitable apparatus) optionally receivesinformation from a user terminal. For example, the SNP may receive userterminal capabilities and location information.

At block 904, the generation of a satellite and beam transition table istriggered at the SNP (or other suitable apparatus). For example, thegeneration of the table may be triggered based on handoff of a userterminal to a satellite or based on receipt of a measurement messagefrom the user terminal.

At block 906, the SNP (or other suitable apparatus) generates asatellite and beam transition table that indicates timing fortransitioning between beams and satellites. In some aspects, the tableis optionally based, in part, on information received from the userterminal at block 902.

At block 908, the SNP (or other suitable apparatus) sends the satelliteand beam transition table to the user terminal.

At block 910, the SNP (or other suitable apparatus) performs handoffsfor the user terminal to different beams and at least one satellitebased on the satellite and beam transition table.

FIG. 10 is a diagram illustrating an example of a process 1000 for usinga satellite and beam transition table in accordance with some aspects ofthe disclosure. The process 1000 may take place within a processingcircuit which may be located in a user terminal or some other suitableapparatus (device). In some implementations, the process 1000 representsoperations performed by the control processor 420 of FIG. 4. In someimplementations, the process 1000 represents operations performed by theapparatus 2200 of FIG. 22 (e.g., by the processing circuit 2210). Ofcourse, in various aspects within the scope of the disclosure, theprocess 1000 may be implemented by any suitable apparatus capable ofsupporting communication-related operations.

At block 1002, a user terminal (or other suitable apparatus) optionallysends a measurement message.

At block 1004, the user terminal (or other suitable apparatus) receivesa satellite and beam transition table that indicates timing fortransitioning between beams and satellites.

At block 1006, the user terminal (or other suitable apparatus) performshandoffs to different beams and at least one satellite based on thesatellite and beam transition table.

FIG. 11 is a diagram illustrating an example of a process 1100 forsignaling user terminal capability information in accordance with someaspects of the disclosure. The process 1100 may take place within aprocessing circuit which may be located in a user terminal or some othersuitable apparatus (device). In some implementations, the process 1100represents operations performed by the control processor 420 of FIG. 4.In some implementations, the process 1100 represents operationsperformed by the apparatus 2200 of FIG. 22 (e.g., by the processingcircuit 2210). Of course, in various aspects within the scope of thedisclosure, the process 1100 may be implemented by any suitableapparatus capable of supporting communication-related operations.

At block 1102, the transmission of user terminal capability informationis triggered at a user terminal (or other suitable apparatus). Forexample, the transmission may be triggered as a result of an initialconnection to a satellite.

At block 1104, the user terminal (or other suitable apparatus) generatesa capabilities message. In some aspects, the message indicates whetherthe UT can sense multiple beams/satellites and/or the message indicatesUT inter-beam/inter-satellite tune time.

At block 1106, the user terminal (or other suitable apparatus) sends thecapabilities message to an SNP.

FIG. 12 is a diagram illustrating an example of a process 1200 for usinguser terminal capabilities in accordance with some aspects of thedisclosure. The process 1200 may take place within a processing circuitwhich may be located in an SNP or some other suitable apparatus(device). In some implementations, the process 1200 representsoperations performed by the SNP controller 250 of FIG. 2. In someimplementations, the process 1200 represents operations performed by theapparatus 2000 of FIG. 20 (e.g., by the processing circuit 2010). Ofcourse, in various aspects within the scope of the disclosure, theprocess 1200 may be implemented by any suitable apparatus capable ofsupporting communication-related operations.

At block 1202, an SNP (or other suitable apparatus) receives acapabilities message from a user terminal. This capabilities messageincludes user terminal capability information.

At block 1204, the SNP (or other suitable apparatus) generates asatellite and beam transition table. In some aspects, the table isgenerated based, in part, on the user terminal capability information(e.g., tune times), user terminal location information, satellitemotion, ephemeris information, and a restriction due to incumbentsystems.

At block 1206, the SNP (or other suitable apparatus) selects a handoffprocedure for the user terminal based, in part, on the user terminalcapability information. For example, monitoring for a measurementmessage from a user terminal may be enabled or disabled based on whetherthe user terminal is dual sense capable. Thus, an apparatus may enableor disable whether the apparatus monitors for a measurement messagebased on the user terminal capability information.

FIG. 13 is a diagram illustrating an example of a process 1300 forsignaling user terminal location information in accordance with someaspects of the disclosure. The process 1300 may take place within aprocessing circuit which may be located in a user terminal or some othersuitable apparatus (device). In some implementations, the process 1300represents operations performed by the control processor 420 of FIG. 4.In some implementations, the process 1300 represents operationsperformed by the apparatus 2200 of FIG. 22 (e.g., by the processingcircuit 2210). Of course, in various aspects within the scope of thedisclosure, the process 1300 may be implemented by any suitableapparatus capable of supporting communication-related operations.

At block 1302, the transmission of user terminal location information istriggered at a user terminal (or other suitable apparatus). This may bethe result of an initial connection, or based on whether the UT isbeyond a geographical boundary (geo-fencing), or based on whether anerror bound has been exceeded.

At block 1304, the user terminal (or other suitable apparatus) generatesa location message. In some aspects, the message may indicate thecurrent location if the UT is stationary, or indicate a motion vector ifthe UT is moving.

At block 1306, the user terminal (or other suitable apparatus) sends thelocation message to an SNP.

FIG. 14 is a diagram illustrating an example of a process 1400 for usinguser terminal location information in accordance with some aspects ofthe disclosure. The process 1400 may take place within a processingcircuit which may be located in an SNP or some other suitable apparatus(device). In some implementations, the process 1400 representsoperations performed by the SNP controller 250 of FIG. 2. In someimplementations, the process 1400 represents operations performed by theapparatus 2000 of FIG. 20 (e.g., by the processing circuit 2010). Ofcourse, in various aspects within the scope of the disclosure, theprocess 1400 may be implemented by any suitable apparatus capable ofsupporting communication-related operations.

At block 1402, an SNP (or other suitable apparatus) receives a locationmessage from a user terminal. This location message includes userterminal location information.

At block 1404, the SNP (or other suitable apparatus) generates asatellite and beam transition table based, in part, on user terminallocation information. For example, if the UT is stationary, the SNP maygenerate the table based on the current UT location. As another example,if the UT is moving, the SNP may generate the table based on a UT motionvector.

FIG. 15 is a diagram illustrating an example of a user terminal handoffprocess 1500 in accordance with some aspects of the disclosure. Theprocess 1500 may take place within a processing circuit which may belocated in a user terminal or some other suitable apparatus (device). Insome implementations, the process 1500 represents operations performedby the control processor 420 of FIG. 4. In some implementations, theprocess 1500 represents operations performed by the apparatus 2200 ofFIG. 22 (e.g., by the processing circuit 2210). Of course, in variousaspects within the scope of the disclosure, the process 1500 may beimplemented by any suitable apparatus capable of supportingcommunication-related operations.

At block 1502, an upcoming user terminal handoff is indicated at a userterminal (or other suitable apparatus). For example, the handoff may beindicated based on a satellite and beam transition table.

At block 1504, the user terminal (or other suitable apparatus) measuressatellite signals (e.g., signals from the satellites indicated in thetable).

At block 1506, the user terminal (or other suitable apparatus)determines whether to send a measurement message. In some aspects, thisdetermination may involve determining whether signals from the currentsatellite/beam or the target satellite/beam are inadequate.

At block 1508, if applicable, the user terminal (or other suitableapparatus) sends a measurement message and receives a new satellite andbeam transition table. In some aspects, the message may includemeasurement data and/or a request to advance/retard handoff timing.Thus, in some aspects, the user terminal may send a measurement messagebased on the signals measured at block 1504 and receive the table as aresult of sending the measurement message.

At block 1510, the user terminal (or other suitable apparatus) hands-offto the target satellite/beam according to the satellite and beamtransition table.

FIG. 16 is a diagram illustrating an example of an SNP handoff process1600 in accordance with some aspects of the disclosure. The process 1600may take place within a processing circuit which may be located in anSNP or some other suitable apparatus (device). In some implementations,the process 1600 represents operations performed by the SNP controller250 of FIG. 2. In some implementations, the process 1600 representsoperations performed by the apparatus 2000 of FIG. 20 (e.g., by theprocessing circuit 2010). Of course, in various aspects within the scopeof the disclosure, the process 1600 may be implemented by any suitableapparatus capable of supporting communication-related operations.

At block 1602, an SNP (or other suitable apparatus) receives ameasurement message from a user terminal.

At block 1604, the SNP (or other suitable apparatus) determines, basedon the measurement message, whether to modify the satellite and beamtransition table.

At block 1606, if applicable, the SNP (or other suitable apparatus)modifies the satellite and beam transition table (e.g., advances orretards transition timing) and sends the modified table to the userterminal.

At block 1608, the SNP (or other suitable apparatus) conducts a handoffof the user terminal according to the satellite and beam transitiontable.

FIG. 17 is a diagram illustrating another example of an inter-satellitehandoff signaling process 1700 in accordance with some aspects of thedisclosure. The process 1700 may take place within a processing circuitwhich may be located in an SNP, a user terminal, or some other suitableapparatuses (devices). In some implementations, the process 1700represents one or more operations performed by the SNP controller 250 ofFIG. 2. In some implementations, the process 1700 represents one or moreoperations performed by the control processor 420 of FIG. 4. In someimplementations, the process 1700 represents one or more operationsperformed by the apparatus 2000 of FIG. 20 (e.g., by the processingcircuit 2010). In some implementations, the process 1700 represents oneor more operations performed by the apparatus 2200 of FIG. 22 (e.g., bythe processing circuit 2210). Of course, in various aspects within thescope of the disclosure, the process 1700 may be implemented by anysuitable apparatuses capable of supporting communication-relatedoperations.

At block 1702, a user terminal (or other suitable apparatus) connects toa first satellite controlled by a first NAC at an SNP.

At block 1704, handoff of the user terminal (or other suitableapparatus) to a second satellite controlled by a second NAC at the SNPis indicated.

At block 1706, the second NAC (or other suitable apparatus) generates asatellite and beam transition table for the user terminal.

At block 1708, the second NAC (or other suitable apparatus) sends thesatellite and beam transition table to the first NAC.

At block 1710, the first NAC (or other suitable apparatus) sends thesatellite and beam transition table to the user terminal.

At block 1712, the user terminal (or other suitable apparatus) ishanded-off to a second satellite according to the satellite and beamtransition table.

FIG. 18 is a diagram illustrating an example of a process 1800 forsignaling ephemeris information in accordance with some aspects of thedisclosure. The process 1800 may take place within a processing circuitwhich may be located in an SNP, a user terminal, or some other suitableapparatuses (devices). In some implementations, the process 1800represents one or more operations performed by the SNP controller 250 ofFIG. 2. In some implementations, the process 1800 represents one or moreoperations performed by the control processor 420 of FIG. 4. In someimplementations, the process 1800 represents one or more operationsperformed by the apparatus 2000 of FIG. 20 (e.g., by the processingcircuit 2010). In some implementations, the process 1800 represents oneor more operations performed by the apparatus 2200 of FIG. 22 (e.g., bythe processing circuit 2210). Of course, in various aspects within thescope of the disclosure, the process 1800 may be implemented by anysuitable apparatuses capable of supporting communication-relatedoperations.

At block 1802, an SNP (or other suitable apparatus) sends ephemerisinformation to a user terminal.

At block 1804, the user terminal (or other suitable apparatus) receivesthe ephemeris information.

At block 1806, the user terminal (or other suitable apparatus) uses theephemeris information to synchronize with a satellite.

FIG. 19 is a diagram illustrating an example of a radio link failureprocess 1900 in accordance with some aspects of the disclosure. Theprocess 1900 may take place within a processing circuit which may belocated in a user terminal or some other suitable apparatus (device). Insome implementations, the process 1900 represents operations performedby the control processor 420 of FIG. 4. In some implementations, theprocess 1900 represents operations performed by the apparatus 2200 ofFIG. 22 (e.g., by the processing circuit 2210). Of course, in variousaspects within the scope of the disclosure, the process 1900 may beimplemented by any suitable apparatus capable of supportingcommunication-related operations.

At block 1902, a user terminal (or other suitable apparatus) losesconnectivity to a satellite and/or beam.

At block 1904, the user terminal (or other suitable apparatus) entersradio link failure mode.

At block 1906, the user terminal (or other suitable apparatus)identifies an alternate satellite and/or beam (e.g., based on ephemerisinformation stored at the user terminal).

At block 1908, the user terminal (or other suitable apparatus)establishes a connection using the alternate satellite and/or beam.

At block 1910, the user terminal (or other suitable apparatus)communicates with an SNP via the new connection.

At block 1912, the user terminal (or other suitable apparatus) exitsradio link failure mode.

Example Apparatus

FIG. 20 illustrates a block diagram of an example hardwareimplementation of an apparatus 2000 configured to communicate accordingto one or more aspects of the disclosure. For example, the apparatus2000 could embody or be implemented within an SNP or some other type ofdevice that supports satellite communication. Thus, in some aspects, theapparatus 2000 could be an example of the SNP 200 or the SNP 201 ofFIG. 1. In various implementations, the apparatus 2000 could embody orbe implemented within a gateway, a ground station, a vehicularcomponent, or any other electronic device having circuitry.

The apparatus 2000 includes a communication interface (e.g., at leastone transceiver) 2002, a storage medium 2004, a user interface 2006, amemory device (e.g., a memory circuit) 2008, and a processing circuit(e.g., at least one processor) 2010. In various implementations, theuser interface 2006 may include one or more of: a keypad, a display, aspeaker, a microphone, a touchscreen display, of some other circuitryfor receiving an input from or sending an output to a user.

These components can be coupled to and/or placed in electricalcommunication with one another via a signaling bus or other suitablecomponent, represented generally by the connection lines in FIG. 20. Thesignaling bus may include any number of interconnecting buses andbridges depending on the specific application of the processing circuit2010 and the overall design constraints. The signaling bus linkstogether various circuits such that each of the communication interface2002, the storage medium 2004, the user interface 2006, and the memorydevice 2008 are coupled to and/or in electrical communication with theprocessing circuit 2010. The signaling bus may also link various othercircuits (not shown) such as timing sources, peripherals, voltageregulators, and power management circuits, which are well known in theart, and therefore, will not be described any further.

The communication interface 2002 provides a means for communicating withother apparatuses over a transmission medium. In some implementations,the communication interface 2002 includes circuitry and/or programmingadapted to facilitate the communication of information bi-directionallywith respect to one or more communication devices in a network. In someimplementations, the communication interface 2002 is adapted tofacilitate wireless communication of the apparatus 2000. In theseimplementations, the communication interface 2002 may be coupled to oneor more antennas 2012 as shown in FIG. 20 for wireless communicationwithin a wireless communication system. The communication interface 2002can be configured with one or more standalone receivers and/ortransmitters, as well as one or more transceivers. In the illustratedexample, the communication interface 2002 includes a transmitter 2014and a receiver 2016. The communication interface 2002 serves as oneexample of a means for receiving and/or means transmitting.

The memory device 2008 may represent one or more memory devices. Asindicated, the memory device 2008 may maintain satellite-relatedinformation 2018 along with other information used by the apparatus2000. In some implementations, the memory device 2008 and the storagemedium 2004 are implemented as a common memory component. The memorydevice 2008 may also be used for storing data that is manipulated by theprocessing circuit 2010 or some other component of the apparatus 2000.

The storage medium 2004 may represent one or more computer-readable,machine-readable, and/or processor-readable devices for storingprogramming, such as processor executable code or instructions (e.g.,software, firmware), electronic data, databases, or other digitalinformation. The storage medium 2004 may also be used for storing datathat is manipulated by the processing circuit 2010 when executingprogramming. The storage medium 2004 may be any available media that canbe accessed by a general purpose or special purpose processor, includingportable or fixed storage devices, optical storage devices, and variousother mediums capable of storing, containing or carrying programming

By way of example and not limitation, the storage medium 2004 mayinclude a magnetic storage device (e.g., hard disk, floppy disk,magnetic strip), an optical disk (e.g., a compact disc (CD) or a digitalversatile disc (DVD)), a smart card, a flash memory device (e.g., acard, a stick, or a key drive), a random access memory (RAM), a readonly memory (ROM), a programmable ROM (PROM), an erasable PROM (EPROM),an electrically erasable PROM (EEPROM), a register, a removable disk,and any other suitable medium for storing software and/or instructionsthat may be accessed and read by a computer. The storage medium 2004 maybe embodied in an article of manufacture (e.g., a computer programproduct). By way of example, a computer program product may include acomputer-readable medium in packaging materials. In view of the above,in some implementations, the storage medium 2004 may be a non-transitory(e.g., tangible) storage medium.

The storage medium 2004 may be coupled to the processing circuit 2010such that the processing circuit 2010 can read information from, andwrite information to, the storage medium 2004. That is, the storagemedium 2004 can be coupled to the processing circuit 2010 so that thestorage medium 2004 is at least accessible by the processing circuit2010, including examples where at least one storage medium is integralto the processing circuit 2010 and/or examples where at least onestorage medium is separate from the processing circuit 2010 (e.g.,resident in the apparatus 2000, external to the apparatus 2000,distributed across multiple entities, etc.).

Programming stored by the storage medium 2004, when executed by theprocessing circuit 2010, causes the processing circuit 2010 to performone or more of the various functions and/or process operations describedherein. For example, the storage medium 2004 may include operationsconfigured for regulating operations at one or more hardware blocks ofthe processing circuit 2010, as well as to utilize the communicationinterface 2002 for wireless communication utilizing their respectivecommunication protocols.

The processing circuit 2010 is generally adapted for processing,including the execution of such programming stored on the storage medium2004. As used herein, the terms “code” or “programming” shall beconstrued broadly to include without limitation instructions,instruction sets, data, code, code segments, program code, programs,programming, subprograms, software modules, applications, softwareapplications, software packages, routines, subroutines, objects,executables, threads of execution, procedures, functions, etc., whetherreferred to as software, firmware, middleware, microcode, hardwaredescription language, or otherwise.

The processing circuit 2010 is arranged to obtain, process and/or senddata, control data access and storage, issue commands, and control otherdesired operations. The processing circuit 2010 may include circuitryconfigured to implement desired programming provided by appropriatemedia in at least one example. For example, the processing circuit 2010may be implemented as one or more processors, one or more controllers,and/or other structure configured to execute executable programming.Examples of the processing circuit 2010 may include a general purposeprocessor, a digital signal processor (DSP), an application specificintegrated circuit (ASIC), a field programmable gate array (FPGA) orother programmable logic component, discrete gate or transistor logic,discrete hardware components, or any combination thereof designed toperform the functions described herein. A general purpose processor mayinclude a microprocessor, as well as any conventional processor,controller, microcontroller, or state machine. The processing circuit2010 may also be implemented as a combination of computing components,such as a combination of a DSP and a microprocessor, a number ofmicroprocessors, one or more microprocessors in conjunction with a DSPcore, an ASIC and a microprocessor, or any other number of varyingconfigurations. These examples of the processing circuit 2010 are forillustration and other suitable configurations within the scope of thedisclosure are also contemplated.

According to one or more aspects of the disclosure, the processingcircuit 2010 may be adapted to perform any or all of the features,processes, functions, operations and/or routines for any or all of theapparatuses described herein. For example, the processing circuit 2010may be configured to perform any of the steps, functions, and/orprocesses described with respect to FIGS. 7-9, 12, 14, and 16-18. Asused herein, the term “adapted” in relation to the processing circuit2010 may refer to the processing circuit 2010 being one or more ofconfigured, employed, implemented, and/or programmed to perform aparticular process, function, operation and/or routine according tovarious features described herein.

The processing circuit 2010 may be a specialized processor, such as anapplication specific integrated circuit (ASIC) that serves as a meansfor (e.g., structure for) carrying out any one of the operationsdescribed in conjunction with FIGS. 7-9, 12, 14, and 16-18. Theprocessing circuit 2010 serves as one example of a means fortransmitting and/or a means for receiving. In some implementations, theprocessing circuit 2010 incorporates the functionality of the SNPcontroller 250 of FIG. 2.

According to at least one example of the apparatus 2000, the processingcircuit 2010 may include one or more of a circuit/module for generating2020, a circuit/module for sending 2022, a circuit/module for performinghandoffs 2024, a circuit/module for receiving 2026, a circuit/module fordetermining whether to modify 2028, a circuit/module for selecting 2030,a circuit/module for determining a time 2032, or a circuit/module fortransferring 2034. In various implementations, the circuit/module forgenerating 2020, the circuit/module for sending 2022, the circuit/modulefor performing handoffs 2024, the circuit/module for receiving 2026, thecircuit/module for determining whether to modify 2028, thecircuit/module for selecting 2030, the circuit/module for determining atime 2032, and the circuit/module for transferring 2034 may correspond,at least in part, to the SNP controller 250 of FIG. 2.

The circuit/module for generating 2020 may include circuitry and/orprogramming (e.g., code for generating 2036 stored on the storage medium2004) adapted to perform several functions relating to, for example,generating satellite and beam transition information that specifies atime to start and a time to terminate communication with a particularbeam of a particular satellite. In some implementations, thecircuit/module for generating 2020 calculates the information (e.g., thedata for Table 1) based on satellite ephemeris data and user terminallocation data. To this end, the circuit/module for generating 2020collects this data, processes the data to generate the information andsends the information to a component of the apparatus 2000 (e.g., thememory device 2008). For example, for a given location of a userterminal, the circuit/module for generating 2020 can determine when aparticular beam of a particular satellite will provide coverage for theuser terminal based on the location of the satellite and thedirectionality and coverage of the beams of the satellite over time.

The circuit/module for sending 2022 may include circuitry and/orprogramming (e.g., code for sending 2038 stored on the storage medium2004) adapted to perform several functions relating to, for example,sending information (e.g., data) to another apparatus. Initially, thecircuit/module for sending 2022 obtains the information to be sent(e.g., from the memory device 2008, the circuit/module for generating2020, or some other component). In various implementations, theinformation to be sent may include satellite and beam transitioninformation to be sent to a user terminal. The circuit/module forsending 2022 may then format the information for sending (e.g., in amessage, according to a protocol, etc.). The circuit/module for sending2022 then causes the information to be sent via a wireless communicationmedium (e.g., via satellite signaling). To this end, the circuit/modulefor sending 2022 may send the data to the communication interface 2002(e.g., a digital subsystem or an RF subsystem) or some other componentfor transmission. In some implementations, the communication interface2002 includes the circuit/module for sending 2022 and/or the code forsending 2038.

The circuit/module for performing handoffs 2024 may include circuitryand/or programming (e.g., code for performing handoffs 2040 stored onthe storage medium 2004) adapted to perform several functions relatingto, for example, performing handoffs for a user terminal to differentbeams and at least one satellite. In some implementations, thecircuit/module for performing handoffs 2024 identifies the targetsatellite and/or the target beam based on the satellite and beamtransition information (e.g., Table 1). To this end, the circuit/modulefor performing handoffs 2024 collects this information, processes theinformation to identify the target, and reconfigures its communicationparameters to cause communication with the user terminal to be conductedvia the target. For example, for a given location of a user terminal,the circuit/module for performing handoffs 2024 can determine whether aparticular beam of a particular satellite would provide sufficientcoverage for the user terminal based on the location of the satelliteand the directionality and coverage of the beams of the satellite overtime. If the satellite/beam would provide sufficient coverage, thecircuit/module for performing handoffs 2024 can designate thatsatellite/beam as the target for the handoff and commence handoffsignaling accordingly.

The circuit/module for receiving 2026 may include circuitry and/orprogramming (e.g., code for receiving 2042 stored on the storage medium2004) adapted to perform several functions relating to, for example,receiving information (e.g., data) from another apparatus. In variousimplementations, the information to be received may include ameasurement message from a user terminal. Initially, the circuit/modulefor receiving 2026 obtains received information. For example, thecircuit/module for receiving 2026 may obtain this information from acomponent of the apparatus 2000 (e.g., the communication interface 2002(e.g., a digital subsystem or an RF subsystem), the memory device 2008,or some other component) or directly from a device (e.g., a satellite)that relayed the information from the user terminal. In someimplementations, the circuit/module for receiving 2026 identifies amemory location of a value in the memory device 2008 and invokes a readof that location. In some implementations, the circuit/module forreceiving 2026 processes (e.g., decodes) the received information. Thecircuit/module for receiving 2026 outputs the received information(e.g., stores the received information in the memory device 2008 orsends the information to another component of the apparatus 2000). Insome implementations, the communication interface 2002 includes thecircuit/module for receiving 2026 and/or the code for receiving 2042.

The circuit/module for determining whether to modify 2028 may includecircuitry and/or programming (e.g., code for determining whether tomodify 2044 stored on the storage medium 2004) adapted to performseveral functions relating to, for example, determining whether tomodify the satellite and beam transition information. In someimplementations, the circuit/module for determining whether to modify2028 makes this determination based on the received measurement message.To this end, the circuit/module for determining whether to modify 2028collects this measurement message information (e.g., from thecircuit/module for receiving 2026, the memory device 2008, or some othercomponent of the apparatus 2000). The circuit/module for determiningwhether to modify 2028 may then process the information to determinewhether the current timing parameters need to be changed (e.g., due topoor RF conditions or improved RF conditions). For example, thecircuit/module for determining whether to modify 2028 may compare signalquality information contained in a measurement message with one or moresignal quality thresholds. Finally, the circuit/module for determiningwhether to modify 2028 generates an indication of this determination(e.g., indicative of advancement of a handoff or delay of a handoff).

The circuit/module for selecting 2030 may include circuitry and/orprogramming (e.g., code for selecting 2046 stored on the storage medium2004) adapted to perform several functions relating to, for example,selecting a handoff procedure for a user terminal. In someimplementations, the circuit/module for selecting 2030 makes thisdetermination based on capability information received from the userterminal To this end, the circuit/module for selecting 2030 collectsthis capability information, processes the information to identify ahandoff procedure, and generates an indication of this determination.For example, the selection of the handoff procedure may involvedetermining whether the user terminal is dual sense capable, andenabling or disabling monitoring for a measurement message from the userterminal based on whether the user terminal is dual sense capable. Thus,in some implementations, the circuit/module for selecting 2030 acquiresconfiguration information about the user terminal (e.g., from the memorydevice 2008, from the receiver 2016, or from some other component),checks this information to identify the capability of the user terminalto select a supported handoff procedure, and generates an indication ofthis determination (e.g., that is sent to the memory device 2008, thecircuit/module for performing handoffs 2024, or some other component).

The circuit/module for determining a time 2032 may include circuitryand/or programming (e.g., code for determining a time 2048 stored on thestorage medium 2004) adapted to perform several functions relating to,for example, determining a time of handoff of a user terminal. In someimplementations, the circuit/module for determining a time 2032 makesthis determination based on the satellite and beam transitioninformation (e.g., Table 1). To this end, the circuit/module fordetermining a time 2032 acquires this information (e.g., from thecircuit/module for receiving 2026, the memory device 2008, or some othercomponent of the apparatus 2000). The circuit/module for a time 2032 maythen process the information to determine the time (e.g., the framenumber) for the next handoff of the user terminal. For example, thecircuit/module for a time 2032 may compare a current time indication(e.g., a frame number) with the timing indications in Table 1. Thecircuit/module for determining a time 2032 generates an indication ofthis determination (e.g., indicative of the time of handoff) and sendsthe indication to a component of the apparatus 2000 (e.g., thecircuit/module for transferring 2034, the memory device 2008, or someother component).

The circuit/module for transferring 2034 may include circuitry and/orprogramming (e.g., code for transferring 2050 stored on the storagemedium 2004) adapted to perform several functions relating to, forexample, transferring user queues prior to handoff. Initially, thecircuit/module for transferring 2034 receives an indication of a time ofhandoff (e.g., from the memory device 2008, the circuit/module fordetermining a time 2032, or some other component). Next, prior to thetime of handoff, the circuit/module for transferring 2034 obtains queueinformation to be sent (e.g., from the memory device 2008, or some othercomponent). In various implementations, this information may be sent toanother SNP. The circuit/module for transferring 2034 may then formatthe queue information for sending (e.g., in a message, according to aprotocol, etc.). The circuit/module for transferring 2034 then causesthe queue information to be sent via an appropriate communication medium(e.g., via the infrastructure 106 of FIG. 1). To this end, thecircuit/module for transferring 2034 may send the data to thecommunication interface 2002 or some other component for transmission.In some implementations, the communication interface 2002 includes thecircuit/module for transferring 2034 and/or the code for transferring2050.

As mentioned above, programming stored by the storage medium 2004, whenexecuted by the processing circuit 2010, causes the processing circuit2010 to perform one or more of the various functions and/or processoperations described herein. For example, the programming, when executedby the processing circuit 2010, may cause the processing circuit 2010 toperform the various functions, steps, and/or processes described hereinwith respect to FIGS. 7-9, 12, 14, and 16-18 in various implementations.As shown in FIG. 20, the storage medium 2004 may include one or more ofthe code for generating 2036, the code for sending 2038, the code forperforming handoffs 2040, the code for receiving 2042, the code fordetermining whether to modify 2044, the code for selecting 2046, thecode for determining a time 2048, or the code for transferring 2050.

Example Process

FIG. 21 illustrates a process 2100 for communication in accordance withsome aspects of the disclosure. The process 2100 may take place within aprocessing circuit (e.g., the processing circuit 2010 of FIG. 20), whichmay be located in an SNP or some other suitable apparatus. In someimplementations, the process 2100 may be performed by an SNP for atleast one non-geosynchronous satellite. In some implementations, theprocess 2100 represents operations performed by the SNP controller 250of FIG. 2. Of course, in various aspects within the scope of thedisclosure, the process 2100 may be implemented by any suitableapparatus capable of supporting communication operations.

At block 2102, an apparatus (e.g., an SNP) generates satellite and beamtransition information that specifies a time to start and a time toterminate communication with a particular beam of a particularsatellite. In some aspects, the operations of block 2102 may correspondto the operations of block 906 of FIG. 9.

In some aspects, the satellite and beam transition information isgenerated based on at least one of: capabilities information for theuser terminal, location information for the user terminal, ephemerisinformation, or a restriction due to an incumbent system. In someaspects, the capabilities information indicates at least one of: whetherthe user terminal can sense multiple beams, whether the user terminalcan sense multiple satellites, an inter-beam tune time for the userterminal, or an inter-satellite tune time for the user terminal. In someaspects, the location information includes a current location for theuser terminal or a motion vector for the user terminal.

In some aspects, the generation of the satellite and beam transitioninformation is triggered based on at least one of: handoff of the userterminal to a different satellite, or receipt of a measurement messagefrom the user terminal.

In some implementations, the circuit/module for generating 2020 of FIG.20 performs the operations of block 2102. In some implementations, thecode for generating 2036 of FIG. 20 is executed to perform theoperations of block 2102.

At block 2104, the apparatus sends the satellite and beam transitioninformation to a user terminal. In some aspects, this information issent via a satellite. In some aspects, the operations of block 2104 maycorrespond to the operations of block 908 of FIG. 9.

In some implementations, the circuit/module for sending 2022 of FIG. 20performs the operations of block 2104. In some implementations, the codefor sending 2038 of FIG. 20 is executed to perform the operations ofblock 2104.

In some aspects, the process 2100 further includes performing handoffsfor the user terminal to different beams and at least one satellitebased on the satellite and beam transition information. In some aspects,these operations may correspond to the operations of block 910 of FIG.9. In some implementations, the circuit/module for performing handoffs2024 of FIG. 20 performs these operations. In some implementations, thecode for performing handoffs 2040 of FIG. 20 is executed to performthese operations.

In some aspects, the process 2100 further includes receiving ameasurement message from the user terminal; and determining, based onthe measurement message, whether to modify the satellite and beamtransition information. In some aspects, the modification of thesatellite and beam transition information includes advancing a handoffor delaying a handoff. In some aspects, these operations may correspondto the operations of blocks 1602 and 1604 of FIG. 16. In someimplementations, the circuit/module for receiving 2026 and/or thecircuit/module for determining whether to modify 2028 of FIG. 20performs these operations. In some implementations, the code forreceiving 2042 and/or the code for determining whether to modify 2044 ofFIG. 20 is executed to perform these operations.

In some aspects, the process 2100 further includes selecting a handoffprocedure for the user terminal based on capability information receivedfrom the user terminal. In some aspects, the selection of the handoffprocedure includes enabling or disabling monitoring for a measurementmessage from the user terminal based on whether the user terminal isdual sense capable. In some aspects, these operations may correspond tothe operations of block 1206 of FIG. 12. In some implementations, thecircuit/module for selecting 2030 of FIG. 20 performs these operations.In some implementations, the code for selecting 2046 of FIG. 20 isexecuted to perform these operations.

In some aspects, the process 2100 further includes determining a time ofa handoff of the user terminal and transferring user queues prior to thehandoff. In some implementations, the circuit/module for determining atime 2032 and/or the circuit/module for transferring 2034 of FIG. 20performs these operations. In some implementations, the code fordetermining a time 2048 and/or the code for transferring 2050 of FIG. 20is executed to perform these operations.

Example Apparatus

FIG. 22 illustrates a block diagram of an example hardwareimplementation of another apparatus 2200 configured to communicateaccording to one or more aspects of the disclosure. For example, theapparatus 2200 could embody or be implemented within a UT or some othertype of device that supports wireless communication. Thus, in someaspects, the apparatus 2200 could be an example of the UT 400 or the UT401 of FIG. 1. In various implementations, the apparatus 2200 couldembody or be implemented within a mobile phone, a smart phone, a tablet,a portable computer, a server, a personal computer, a sensor, anentertainment device, a vehicular component, medical devices, or anyother electronic device having circuitry.

The apparatus 2200 includes a communication interface (e.g., at leastone transceiver) 2202, a storage medium 2204, a user interface 2206, amemory device 2208 (e.g., storing satellite-related information 2218),and a processing circuit (e.g., at least one processor) 2210. In variousimplementations, the user interface 2206 may include one or more of: akeypad, a display, a speaker, a microphone, a touchscreen display, ofsome other circuitry for receiving an input from or sending an output toa user. The communication interface 2202 may be coupled to one or moreantennas 2212, and may include a transmitter 2214 and a receiver 2216.In general, the components of FIG. 22 may be similar to correspondingcomponents of the apparatus 2000 of FIG. 20.

According to one or more aspects of the disclosure, the processingcircuit 2210 may be adapted to perform any or all of the features,processes, functions, operations and/or routines for any or all of theapparatuses described herein. For example, the processing circuit 2210may be configured to perform any of the steps, functions, and/orprocesses described with respect to FIGS. 7, 8, 10, 11, 13, 15, and17-19. As used herein, the term “adapted” in relation to the processingcircuit 2210 may refer to the processing circuit 2210 being one or moreof configured, employed, implemented, and/or programmed to perform aparticular process, function, operation and/or routine according tovarious features described herein.

The processing circuit 2210 may be a specialized processor, such as anapplication specific integrated circuit (ASIC) that serves as a meansfor (e.g., structure for) carrying out any one of the operationsdescribed in conjunction with FIGS. 7, 8, 10, 11, 13, 15, and 17-19. Theprocessing circuit 2210 serves as one example of a means fortransmitting and/or a means for receiving. In various implementations,the processing circuit 2210 may incorporate the functionality of thecontrol processor 420 of FIG. 4.

According to at least one example of the apparatus 2200, the processingcircuit 2210 may include one or more of a circuit/module for receiving2220, a circuit/module for performing handoffs 2222, a circuit/modulefor measuring signals 2224, a circuit/module for sending 2226, or acircuit/module for determining whether to send 2228. In variousimplementations, the circuit/module for receiving 2220, thecircuit/module for performing handoffs 2222, the circuit/module formeasuring signals 2224, the circuit/module for sending 2226, and thecircuit/module for determining whether to send 2228 may correspond, atleast in part, to the control processor 420 of FIG. 4.

The circuit/module for receiving 2220 may include circuitry and/orprogramming (e.g., code for receiving 2230 stored on the storage medium2204) adapted to perform several functions relating to, for example,receiving information (e.g., data) from another apparatus. In variousimplementations, the information to be received may include satelliteand beam transition information that specifies a time to start and atime to terminate communication with a particular beam of a particularsatellite. Initially, the circuit/module for receiving 2220 obtainsreceived information. For example, the circuit/module for receiving 2220may obtain this information from a component of the apparatus 2200 ordirectly from a device (e.g., a satellite) that relayed the informationfrom an SNP. In the former case, the circuit/module for receiving 2220may obtain this information from the communication interface 2202 (e.g.,a UT transceiver as described above for the UT 400 of FIG. 4), thememory device 2208, or some other component. In some implementations,the circuit/module for receiving 2220 identifies a memory location of avalue in the memory device 2208 and invokes a read of that location. Insome implementations, the circuit/module for receiving 2220 processes(e.g., decodes) the received information. The circuit/module forreceiving 2220 outputs the received information (e.g., sends thereceived information to the memory device 2208, the circuit/module forperforming handoffs 2222, or some other component of the apparatus2200). In some implementations, the communication interface 2202includes the circuit/module for receiving 2220 and/or the code forreceiving 2230.

The circuit/module for performing handoffs 2222 may include circuitryand/or programming (e.g., code for performing handoffs 2232 stored onthe storage medium 2204) adapted to perform several functions relatingto, for example, performing handoff to a particular beam of a particularsatellite. In some implementations, the circuit/module for performinghandoffs 2222 identifies a particular beam of a particular satellitebased on satellite and beam transition information (e.g., Table 1). Tothis end, the circuit/module for performing handoffs 2222 collects thisinformation, processes the information to identify the satellite andbeam, and reconfigures its communication parameters to causecommunication with an SNP to be conducted via the identified satelliteand beam. For example, at a particular point in time, the circuit/modulefor performing handoffs 2222 can use the information in Table 1 todetermine whether the user terminal should switch to a differentsatellite beam. As another example, triggers may be set up atbeam/satellite transitions times (e.g., frame numbers) indicated inTable 1.

The circuit/module for measuring signals 2224 may include circuitryand/or programming (e.g., code for measuring signals 2224 stored on thestorage medium 2204) adapted to perform several functions relating to,for example, receiving and processing signals from at least onesatellite. Initially, the circuit/module for measuring signals 2224receives signals. For example, the circuit/module for measuring signals2224 may obtain signal information from a component of the apparatus2200 or directly from a satellite that transmitted the signals. As anexample of the former case, the circuit/module for measuring signals2224 may obtain signal information from the communication interface 2202(e.g., a UT transceiver as described above for the UT 400 of FIG. 4),the memory device 2208 (e.g., if the received signals have beendigitized), or some other component of the apparatus 2200. Thecircuit/module for measuring signals 2224 then processes the receivedsignals (e.g., to determine at least one signal quality of the signals).Finally, the circuit/module for measuring signals 2224 generates anindication of this measurement and sends the indication to the memorydevice 2208, the circuit/module for sending 2224, or some othercomponent of the apparatus 2200. In some implementations, thecommunication interface 2202 includes the circuit/module for measuringsignals 2224 and/or the code for measuring signals 2234.

The circuit/module for sending 2226 may include circuitry and/orprogramming (e.g., code for sending 2236 stored on the storage medium2204) adapted to perform several functions relating to, for example,sending information (e.g., messages) to another apparatus. Initially,the circuit/module for sending 2226 obtains the information to be sent(e.g., from the memory device 2208, the circuit/module for measuringsignals 2224, or some other component). In various implementations, theinformation to be sent may include a measurement message based onmeasured signals, a message including user terminal capabilityinformation, or a message including user terminal location information.The circuit/module for sending 2226 may format the information forsending (e.g., according to a message format, according to a protocol,etc.). The circuit/module for sending 2226 then causes the informationto be sent via a wireless communication medium (e.g., via satellitesignaling). To this end, the circuit/module for sending 2226 may sendthe data to the communication interface 2202 (e.g., a UT transceiver asdescribed above for the UT 400 of FIG. 4) or some other component fortransmission. In some implementations, the communication interface 2202includes the circuit/module for sending 2226 and/or the code for sending2236.

The circuit/module for determining whether to send 2228 may includecircuitry and/or programming (e.g., code for determining whether to send2238 stored on the storage medium 2204) adapted to perform severalfunctions relating to, for example, determining whether to send amessage. In some implementations, the information to be sent may includea measurement message that is based on measured signals. Initially, thecircuit/module for determining whether to send 2228 obtains informationthat is used to make a send decision (e.g., from the memory device 2208,the circuit/module for measuring signals 2224, or some other component).For example, the circuit/module for determining whether to send 2228 mayobtain signal quality information from the circuit/module for measuringsignals 2224. In this case, the circuit/module for determining whetherto send 2228 may determine whether the signals from a current servingsatellite and/or from a target satellite are inadequate (e.g., bycomparing the signal quality information with a signal qualitythreshold). For example, the sending of a measurement message may betriggered if the signals are inadequate. Finally, the circuit/module fordetermining whether to send 2228 generates an indication of thedetermination and sends the indication to the memory device 2208, thecircuit/module for sending 2226, or some other component of theapparatus 2200.

As mentioned above, programming stored by the storage medium 2204, whenexecuted by the processing circuit 2210, causes the processing circuit2210 to perform one or more of the various functions and/or processoperations described herein. For example, the programming, when executedby the processing circuit 2210, may cause the processing circuit 2210 toperform the various functions, steps, and/or processes described hereinwith respect to FIGS. 7, 8, 10, 11, 13, 15, and 17-19 in variousimplementations. As shown in FIG. 22, the storage medium 2204 mayinclude one or more of the code for receiving 2230, the code forperforming handoffs 2232, the code for measuring signals 2234, the codefor sending 2236, or the code for determining whether to send 2238.

Example Process

FIG. 23 illustrates a process 2300 for communication in accordance withsome aspects of the disclosure. The process 2300 may take place within aprocessing circuit (e.g., the processing circuit 2210 of FIG. 22), whichmay be located in a UT or some other suitable apparatus. In someimplementations, the process 2300 represents operations performed by thecontrol processor 420 of FIG. 4. Of course, in various aspects withinthe scope of the disclosure, the process 2300 may be implemented by anysuitable apparatus capable of supporting communication operations.

At block 2302, an apparatus (e.g., a UT) receives satellite and beamtransition information that specifies a time to start and a time toterminate communication with a particular beam of a particularsatellite. In some aspects, the operations of block 2302 may correspondto the operations of block 1004 of FIG. 10.

In some implementations, the circuit/module for receiving 2220 of FIG.22 performs the operations of block 2302. In some implementations, thecode for receiving 2230 of FIG. 22 is executed to perform the operationsof block 2302.

At block 2304, the apparatus performs handoff to the particular beam ofthe particular satellite based on the satellite and beam transitioninformation. In some aspects, the operations of block 2304 maycorrespond to the operations of block 1006 of FIG. 10.

In some implementations, the circuit/module for performing handoffs 2222of FIG. 22 performs the operations of block 2304. In someimplementations, the code for performing handoffs 2232 of FIG. 22 isexecuted to perform the operations of block 2304.

In some aspects, the process 2300 further includes: measuring signalsfrom at least one satellite; and sending a measurement message based onthe measured signals, wherein the satellite and beam transitioninformation is received as a result of sending the measurement message.In some aspects, the measurement message includes at least one of:measurement data, a request to advance handoff timing, or a request todelay handoff timing. In some aspects, the process 2300 further includesdetermining whether to send the measurement message based on at leastone of: whether signals from a current serving satellite are inadequate,or whether signals from a target satellite are inadequate. In someaspects, these operations may correspond to the operations of blocks1504-1508 of FIG. 15. In some implementations, the circuit/module formeasuring signals 2222 and/or the circuit/module for determining whetherto send 2228 of FIG. 22 performs these operations. In someimplementations, the code for measuring signals 2234 and/or the code fordetermining whether to send 2238 of FIG. 22 is executed to perform theseoperations.

In some aspects, the process 2300 further includes sending a messageincluding user terminal capability information, wherein the satelliteand beam transition information is based on the user terminal capabilityinformation. In some aspects, the user terminal capability informationindicates at least one of: whether a user terminal can sense multiplebeams, whether a user terminal can sense multiple satellites, a userterminal inter-beam tune time, or a user terminal inter-satellite tunetime. In some aspects, the sending of the message including userterminal capability information is triggered as a result of an initialconnection to a satellite. In some aspects, these operations maycorrespond to the operations of blocks 1102-1106 of FIG. 11. In someimplementations, the circuit/module for sending 2226 of FIG. 22 performsthese operations. In some implementations, the code for sending 2236 ofFIG. 22 is executed to perform these operations.

In some aspects, the process 2300 further includes sending a messageincluding user terminal location information, wherein the satellite andbeam transition information is based on the user terminal locationinformation. In some aspects, the user terminal location informationincludes a current user terminal location or a user terminal motionvector. In some aspects, the sending of the message including userterminal location information is triggered as a result of at least oneof: an initial connection to a satellite, whether a user terminal isbeyond a geographical boundary, or whether an error bound has beenexceeded. In some aspects, these operations may correspond to theoperations of blocks 1302-1306 of FIG. 13. In some implementations, thecircuit/module for sending 2226 of FIG. 22 performs these operations. Insome implementations, the code for sending 2236 of FIG. 22 is executedto perform these operations.

Additional Aspects

Many aspects are described in terms of sequences of actions to beperformed by, for example, elements of a computing device. It will berecognized that various actions described herein can be performed byspecific circuits, for example, central processing units (CPUs), graphicprocessing units (GPUs), digital signal processors (DSPs), applicationspecific integrated circuits (ASICs), field programmable gate arrays(FPGAs), or various other types of general purpose or special purposeprocessors or circuits, by program instructions being executed by one ormore processors, or by a combination of both. Additionally, thesesequence of actions described herein can be considered to be embodiedentirely within any form of computer readable storage medium havingstored therein a corresponding set of computer instructions that uponexecution would cause an associated processor to perform thefunctionality described herein. Thus, the various aspects of thedisclosure may be embodied in a number of different forms, all of whichhave been contemplated to be within the scope of the claimed subjectmatter. In addition, for each of the aspects described herein, thecorresponding form of any such aspects may be described herein as, forexample, “logic configured to” perform the described action.

Those of skill in the art will appreciate that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Further, those of skill in the art will appreciate that the variousillustrative logical blocks, modules, circuits, and algorithm stepsdescribed in connection with the aspects disclosed herein may beimplemented as electronic hardware, computer software, or combinationsof both. To clearly illustrate this interchangeability of hardware andsoftware, various illustrative components, blocks, modules, circuits,and steps have been described above generally in terms of theirfunctionality. Whether such functionality is implemented as hardware orsoftware depends upon the particular application and design constraintsimposed on the overall system. Skilled artisans may implement thedescribed functionality in varying ways for each particular application,but such implementation decisions should not be interpreted as causing adeparture from the scope of the disclosure.

The methods, sequences or algorithms described in connection with theaspects disclosed herein may be embodied directly in hardware, in asoftware module executed by a processor, or in a combination of the two.A software module may reside in RAM memory, flash memory, ROM memory,EPROM memory, EEPROM memory, registers, hard disk, a removable disk, aCD-ROM, or any other form of storage medium known in the art. An exampleof a storage medium is coupled to the processor such that the processorcan read information from, and write information to, the storage medium.In the alternative, the storage medium may be integral to the processor.

Accordingly, one aspect of the disclosure can include a computerreadable media embodying a method for time or frequency synchronizationin non-geosynchronous satellite communication systems. Accordingly, thedisclosure is not limited to illustrated examples and any means forperforming the functionality described herein are included in aspects ofthe disclosure.

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any aspect described herein as “exemplary”is not necessarily to be construed as preferred or advantageous overother aspects. Likewise, the term “aspects” does not require that allaspects include the discussed feature, advantage or mode of operation.

The terminology used herein is for the purpose of describing particularaspects only and is not intended to be limiting of the aspects. As usedherein, the singular forms “a,” “an” and “the” are intended to includethe plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises,”“comprising,” “includes” or “including,” when used herein, specify thepresence of stated features, integers, steps, operations, elements, orcomponents, but do not preclude the presence or addition of one or moreother features, integers, steps, operations, elements, components, orgroups thereof. Moreover, it is understood that the word “or” has thesame meaning as the Boolean operator “OR,” that is, it encompasses thepossibilities of “either” and “both” and is not limited to “exclusiveor” (“XOR”), unless expressly stated otherwise. It is also understoodthat the symbol “I” between two adjacent words has the same meaning as“or” unless expressly stated otherwise. Moreover, phrases such as“connected to,” “coupled to” or “in communication with” are not limitedto direct connections unless expressly stated otherwise.

While the foregoing disclosure shows illustrative aspects, it should benoted that various changes and modifications could be made hereinwithout departing from the scope of the appended claims. The functions,steps or actions of the method claims in accordance with aspectsdescribed herein need not be performed in any particular order unlessexpressly stated otherwise. Furthermore, although elements may bedescribed or claimed in the singular, the plural is contemplated unlesslimitation to the singular is explicitly stated.

What is claimed is:
 1. A method of communication, comprising: generatingsatellite and beam transition information that specifies a time to startand a time to terminate communication with a particular beam of aparticular satellite; and sending the satellite and beam transitioninformation to a user terminal.
 2. The method of claim 1, wherein thegeneration of the satellite and beam transition information is based onat least one of: capabilities information for the user terminal,location information for the user terminal, ephemeris information, or arestriction due to an incumbent system.
 3. The method of claim 2,wherein the capabilities information indicates at least one of: whetherthe user terminal can sense multiple beams, whether the user terminalcan sense multiple satellites, an inter-beam tune time for the userterminal, or an inter-satellite tune time for the user terminal.
 4. Themethod of claim 2, wherein the location information comprises a currentlocation for the user terminal or a motion vector for the user terminal.5. The method of claim 1, wherein the generation of the satellite andbeam transition information is triggered based on at least one of:handoff of the user terminal to a different satellite, or receipt of ameasurement message from the user terminal.
 6. The method of claim 1,further comprising: performing handoffs for the user terminal todifferent beams and at least one satellite based on the satellite andbeam transition information.
 7. The method of claim 1, furthercomprising: receiving a measurement message from the user terminal; anddetermining, based on the measurement message, whether to modify thesatellite and beam transition information.
 8. The method of claim 7,wherein the modification of the satellite and beam transitioninformation comprises advancing a handoff or delaying a handoff.
 9. Themethod of claim 1, further comprising: selecting a handoff procedure forthe user terminal based on capability information received from the userterminal.
 10. The method of claim 9, wherein the selection of thehandoff procedure comprises enabling or disabling monitoring for ameasurement message from the user terminal based on whether the userterminal is dual sense capable.
 11. The method of claim 1, performed bya satellite network portal for at least one non-geosynchronoussatellite.
 12. The method of claim 1, further comprising: determining atime of a handoff of the user terminal; and transferring user queuesprior to the handoff.
 13. An apparatus for communication comprising: amemory device; and a processing circuit coupled to the memory device andconfigured to: generate satellite and beam transition information thatspecifies a time to start and a time to terminate communication with aparticular beam of a particular satellite; and send the satellite andbeam transition information to a user terminal.
 14. The apparatus ofclaim 13, wherein the processing circuit is further configured to:generate the satellite and beam transition information based on at leastone of: capabilities information for the user terminal, locationinformation for the user terminal, ephemeris information, or arestriction due to an incumbent system.
 15. The apparatus of claim 14,wherein the capabilities information indicates at least one of: whetherthe user terminal can sense multiple beams, whether the user terminalcan sense multiple satellites, an inter-beam tune time for the userterminal, or an inter-satellite tune time for the user terminal.
 16. Theapparatus of claim 13, wherein the processing circuit is furtherconfigured to: perform handoffs for the user terminal to different beamsand at least one satellite based on the satellite and beam transitioninformation.
 17. The apparatus of claim 13, wherein the processingcircuit is further configured to: receive a measurement message from theuser terminal; and determine, based on the measurement message, whetherto modify the satellite and beam transition information.
 18. Theapparatus of claim 17, wherein, to modify the satellite and beamtransition information, the processing circuit is further configured toadvance a handoff or delay a handoff.
 19. The apparatus of claim 13,wherein the processing circuit is further configured to: select ahandoff procedure for the user terminal based on capability informationreceived from the user terminal.
 20. The apparatus of claim 19, wherein,to select the handoff procedure, the processing circuit is furtherconfigured to enable or disable whether the apparatus monitors for ameasurement message from the user terminal based on whether the userterminal is dual sense capable.
 21. The apparatus of claim 13, whereinthe processing circuit is further configured to: determine a time of ahandoff of the user terminal; and transfer user queues prior to thehandoff.
 22. An apparatus for communication comprising: means forgenerating satellite and beam transition information that specifies atime to start and a time to terminate communication with a particularbeam of a particular satellite; and means for sending the satellite andbeam transition information to a user terminal.
 23. The apparatus ofclaim 22, further comprising: means for performing handoffs for the userterminal to different beams and at least one satellite based on thesatellite and beam transition information.
 24. The apparatus of claim22, further comprising: means for receiving a measurement message fromthe user terminal; and means for determining, based on the measurementmessage, whether to modify the satellite and beam transitioninformation.
 25. The apparatus of claim 22, further comprising: meansfor selecting a handoff procedure for the user terminal based oncapability information received from the user terminal.
 26. Theapparatus of claim 22, further comprising: means for determining a timeof a handoff of the user terminal; and means for transferring userqueues prior to the handoff.
 27. A non-transitory computer-readablemedium storing computer-executable code, including code to: generatesatellite and beam transition information that specifies a time to startand a time to terminate communication with a particular beam of aparticular satellite; and send the satellite and beam transitioninformation to a user terminal.
 28. A method of communication,comprising: receiving satellite and beam transition information thatspecifies a time to start and a time to terminate communication with aparticular beam of a particular satellite; and performing handoff to theparticular beam of the particular satellite based on the satellite andbeam transition information.
 29. The method of claim 28, furthercomprising: measuring signals from at least one satellite; and sending ameasurement message based on the measured signals, wherein the satelliteand beam transition information is received as a result of sending themeasurement message.
 30. The method of claim 29, wherein the measurementmessage comprises at least one of: measurement data, a request toadvance handoff timing, or a request to delay handoff timing.
 31. Themethod of claim 29, further comprising: determining whether to send themeasurement message based on at least one of: whether signals from acurrent serving satellite are inadequate, or whether signals from atarget satellite are inadequate.
 32. The method of claim 28, furthercomprising: sending a message comprising user terminal capabilityinformation, wherein the satellite and beam transition information isbased on the user terminal capability information.
 33. The method ofclaim 32, wherein the user terminal capability information indicates atleast one of: whether a user terminal can sense multiple beams, whethera user terminal can sense multiple satellites, a user terminalinter-beam tune time, or a user terminal inter-satellite tune time. 34.The method of claim 32, wherein the sending of the message comprisinguser terminal capability information is triggered as a result of aninitial connection to a satellite.
 35. The method of claim 28, furthercomprising: sending a message comprising user terminal locationinformation, wherein the satellite and beam transition information isbased on the user terminal location information.
 36. The method of claim35, wherein the user terminal location information comprises a currentuser terminal location or a user terminal motion vector.
 37. The methodof claim 35, wherein the sending of the message comprising user terminallocation information is triggered as a result of at least one of: aninitial connection to a satellite, whether a user terminal is beyond ageographical boundary, or whether an error bound has been exceeded. 38.An apparatus for communication comprising: a memory device; and aprocessing circuit coupled to the memory device and configured to:receive satellite and beam transition information that specifies a timeto start and a time to terminate communication with a particular beam ofa particular satellite; and perform handoff to the particular beam ofthe particular satellite based on the satellite and beam transitioninformation.
 39. The apparatus of claim 38, wherein the processingcircuit is further configured to: measure signals from at least onesatellite; and send a measurement message based on the measured signals,wherein the satellite and beam transition information is received as aresult of sending the measurement message.
 40. The apparatus of claim39, wherein the processing circuit is further configured to: determinewhether to send the measurement message based on at least one of:whether signals from a current serving satellite are inadequate, orwhether signals from a target satellite are inadequate.
 41. Theapparatus of claim 38, wherein: the processing circuit is furtherconfigured to send a message comprising user terminal capabilityinformation; and the satellite and beam transition information is basedon the user terminal capability information.
 42. The apparatus of claim41, wherein the user terminal capability information indicates at leastone of: whether a user terminal can sense multiple beams, whether a userterminal can sense multiple satellites, a user terminal inter-beam tunetime, or a user terminal inter-satellite tune time.
 43. The apparatus ofclaim 38, wherein: the processing circuit is further configured to senda message comprising user terminal location information; and thesatellite and beam transition information is based on the user terminallocation information.
 44. The apparatus of claim 43, wherein the sendingof the message comprising user terminal location information istriggered as a result of at least one of: an initial connection to asatellite, whether a user terminal is beyond a geographical boundary, orwhether an error bound has been exceeded.
 45. An apparatus forcommunication comprising: means for receiving satellite and beamtransition information that specifies a time to start and a time toterminate communication with a particular beam of a particularsatellite; and means for performing handoff to the particular beam ofthe particular satellite based on the satellite and beam transitioninformation.
 46. The apparatus of claim 45, further comprising: meansfor measuring signals from at least one satellite; and means for sendinga measurement message based on the measured signals, wherein thesatellite and beam transition information is received as a result ofsending the measurement message.
 47. The apparatus of claim 46, furthercomprising: means for determining whether to send the measurementmessage based on at least one of: whether signals from a current servingsatellite are inadequate, or whether signals from a target satellite areinadequate.
 48. The apparatus of claim 45, further comprising: means forsending a message comprising user terminal capability information,wherein the satellite and beam transition information is based on theuser terminal capability information.
 49. The apparatus of claim 45,further comprising: means for sending a message comprising user terminallocation information, wherein the satellite and beam transitioninformation is based on the user terminal location information.
 50. Anon-transitory computer-readable medium storing computer-executablecode, including code to: receive satellite and beam transitioninformation that specifies a time to start and a time to terminatecommunication with a particular beam of a particular satellite; andperform handoff to the particular beam of the particular satellite basedon the satellite and beam transition information.